【 Weak current College 】 phase and time delay adjustment---Power By 【 China power house network 】

You may find that the adjustment phase settings (usually in the woofer speaker adjustment, if necessary, can also be adjusted on the decoder) will cause the primary speaker/sub woofer speaker integrated sound more balanced. Test will immediately display is improved: you can be in a certain phase to hear more or fewer low-frequency. Change the phase you hear listening room acoustics sound effects arising both sides, so that you are listening to the location of the sound effects will be different. To carry out phase adjustment, you must clear this would bring joys and half results.

Like I said before, you sit in a listening area where the audition of different, let your assistant to adjust a woofer speaker phase (the other one is closed), audition repeatedly until you get the best sound. Then another woofer speaker for the same test, you must first turn off the speakers. Finally, two woofer speakers are turned on, if necessary and then they are more adjustment, you will find this process using a different test software would be more helpful.

Despite the delay adjustment for different purposes, I still use it with phase adjustment back together, because when you adjust the delay parameter, you can also change the phase. Delay can be regarded as a system to display the sub woofer speaker or reduce the woofer speaker signal routing differences between electronic method.
Delay adjustment to different objectives for the professional audio and home audio fields are frequently used. Some people find ignored phase settings, put the effort in the delay would be better organised. In the woofer speaker sound effects of the integration process, the delay can be used to make from the woofer speaker and main speakers at the arrival of direct sound to hear. Know the speed of the voice, you can quickly figure out a variety of positioning mode signal transmission distance of difference (so even if the delay of many), but how do you figure out the figure number 39aof delay?
For this particular situation, suppose front woofer speaker and friendly speaker of a substantial mode enables its audio at the same time get to listen to the location. Calculation of sound from the left, Center, right, and the former woofer speakers to listen to the location of the time (in ms) or distance (in feet or metres). Then calculate the rear woofer speaker delay.

For example, suppose your left and right, in front of the main speaker/subwoofer speakers from the listening position 5 meters, while the rear left overload listen subwoof position 1 m, 5m – 1m = 4m. Therefore you need to make the rear woofer speaker 4m delay. In this way, from the main left and right, front woofer in/sound and rear woofer speaker sound can also reach the listening position.

【 Weak current College 】 multimedia listening environment and power mix---Power By 【 China power house network 】

In the old shaoyou spread in such a view: listening to music, one third of the equipment, seven environment. Many of my friends might think that the words were overkill, however, often heard that an Internet user in 10 sqm cabin bought 12-inch subwoofer, ready to use 200 watts of power to enjoy intensively, tearing pants of bass, it cannot help heart hair tightly, inhaled gasped, at this point, to think of the "one third of the equipment in seven environments", deeply embedded learning them.

This secret, to hear beautiful moving relationship, it is necessary to put the person, the box, the relationship between the environment. And this one, the size of the room and the speaker's power match, is our most neglected issues.

On the environment: a little experiment

To understand the environmental impact of multimedia sound, a little experiment.

A first step, the experiment room size on effect of sound, the sound box moved to the toilet in a song Hotel California, listen to the water Curtain Cave-like sound effects. The second step, the experiment room open on effect of sound, the speaker to move to places no empty furniture House on a piece of celery CAI, listen to what is called. The third step, the speaker to move to put a song in the plain area, to hear him Jay thin throat much color. You can also put the speaker to move to the people's Hall, Notre Dame de Paris ...

Of course, is a joke, not moving anywhere, a sound card capable of simulating various environment sound effect, then, with the extreme sound to hear me, for my part, very often, then you can appreciate the taste of the die.

Then, listen to the music room much? follow now room conditions, it might be a 10 square meters, 20 square meters and the lower limit is a limit of 10 square meters, in particular the following 5 square meters, according to the principles of acoustics, users almost impossible to get good bass, a low frequency band extruding, sounds dull, turbid in the chest, the heart beat of the side effects of stimulus. Therefore, for this condition, do not recommend to invest in multimedia speaker, using headphones. 25 square meters, more than 25 square metres in particular, could not support most of the multimedia speakers, their actual power not enough. These sections will be expanded later.

Random House's listening. Things messy often absorbs excess wave reflection, make the room close to the correct reverb index. Similarly, on the walls to hang some tapestry wool products such as are valid through the cudgel furniture decorations let become irregular, also have immediate effect.

The high roof is fortunate to have some, perceived sense of listening to the sound field of three-dimensional sense on and in depth, but unfortunately real estate ' and does not pay attention to these, in order to save costs, community building storey in 2.6 meters, raise your hands almost chuding, wretched so chilling. The solution is to put the roof also become irregular, such as the use of more complex style chandelier (careful), in addition, hanging various strange service drops must be young people live, in pursuit of a given a voice like that, you have the courage to leave their rooms into a Moleskine small gift show?

For a room on a variety of factors influence to listen, as follows:


The best worst condition settlement
15 ~ 20 m 5 m following discard multimedia speaker
Top high 2.8 meters 2.4 m to improve reflection at the top, such as the pendant lamp, ornaments
Irregular rectangular shape, due to the extremely narrow or a corner to adjust the computer location, set the partition
Display slightly confusing large glass or smooth products linked to cotton or wool shop products
Corner empty corner little empty corner lot, and solid cubic pile up incidentals or acoustical materials

Power and the environment: give me true digital

Discussed the size of the room, the next question naturally fell in power, more power to meet the needs of our stupid?

Every day we face merchants "800 Watt, 1000-Watt" bombing, even a small plastic loudspeaker can also play on 180 Watts of labels. This fool's trick was Japan speakers in Chinese sales of invention, and now is people give as "market without borders", "Bacchus". In fact, just a small concept trick – peak power or music power, 800, 1000, digital marking is speaker at the moment to be able to withstand the maximum power, and the speaker of the General relationship between the power output should be 10: 1 to conversion, and may even reach 16: 1.

What is a peak power, look at the lifter will know that they can break out of the hundreds of pounds of heavy lift the barbell, can only support a few seconds. While the speaker even a few seconds are not supported.

In accordance with real power, our room is about how much is enough?, or sentence, to be an experiment, movers to 1900T2 nominal power is 15W * 2, in the course of the nominal power M200 is 20W * 2, 15 square meters room listening to suffice. If enough sound pressure is not enough, then try to buy United States accurately, 2.1 speakers actually achieve 260W, 5.1 speakers 500W is reached. In the General House of the living-room, the ground shakes. At the recent emerging from the new multimedia, dew A100 callout 50W * 2 of output power, but they deal with the 20 square meters or more room or to some degree. In effect, doubling the power, sound pressure only three DB, therefore, the power of 50W * 2 and 20W * 2 power in most cases, the difference between the sound pressure.

【 Weak current College 】 importance of acoustic design

In recent years, there is increasing concern of acoustics, International Journal of all major forums, discussions on acoustic design is becoming more common. When listening and microphone and flat frequency response, when digital recording solution to the problem of noise of analog era, a new era had arrived for audio. Equipment gap shrinking, but the quality of the recording works basically depends on the recording technology and recording studios and final mix room acoustic design. Therefore, from the objective conditions, acoustical design for recording, than any other factors are important.
Ensure that the control room of the frequency response is flat for mixing and monitoring is very important, but a large portion of the control room did not deal with this. Worse, many people know nothing about it, not knowing ways to solve this problem. Listen for the sound produce distortion, in any case will not be able to make high quality recordings of works. The Studio of design and control room is completely different according to the recording studio working on need-the need for sound field accordingly adjusted, not all of the strong sound absorption. In order to meet the various needs of acoustic source recording, so that the effect of early recordings more perfect.
About sound insulation
In daily life, building or per far away from the street noise pollution sources doubled distance can be reduced noise, 6dB community trees can reduce the noise around 4dB.
(A) the noise propagation
Noise propagation can be in two forms: airborne noise, solid contained noise.
1. airborne noise
Sonic's most basic mode of transmission is airborne, and airborne noise is ambient noise which spreads through the air into the room noise. A fabric with small holes thick metal plate, small area of approximately 13% of metal plates, when a voice against the surface, there will be almost 97% of sound through. Sound propagation through the pore is quite amazing, asubtle cracks can destroy an entire seal acoustic system. Therefore, the room is isolated from the strict seal on airborne noise emitted is very necessary.
2. solid noise load
Sound through the vibration propagation in solid of machinery such as wood, metal, concrete, etc. Because the air transmission of inefficient to bring solid vibration, so solid containing the main source of noise is due to the vibration source contact solid media surface, such as underground generator or some electrical appliances. Solid sound transmission loss ratio of air transmission of small, can spread very far in distance but no major loss of energy. Wood, concrete and other longitudinal vibration about 304.8 m loss around 2dB. If the transmission medium for the iron and steel materials, the loss will be reduced to 20 times.
(Ii) sound processing
Acoustic treatment has many methods, Studio due to its strict on this floor noise, so the use of suspension structure. Suspension structure can greatly improve the sound isolation degree, especially for the Studio in the city. Suspension structure can add rooms and other structural separation, it can be suspended wall and the wall between a cavity and in the cavity fill soft acoustic material, acoustic using cavity absorption, so that the air, solid noise reduction to a minimum. But suspended structure to meet the requirements of the load-bearing structures.
Regarding the diffusion and absorption
Many people get plastered walls of sound-absorbing materials, thought this would be enough to eliminate reflections, because they feel when they clap your hands, so there is no echo, but this reflection on the control of low-frequency has no meaning. The brick and concrete walls, the problem is particularly serious. The more rigid wall, the more reflective.
Most people who blindly believe that a good Studio should do to minimize the reflection of sound absorption. But the shaping of sound field in no way merely refers to the uptakeof reflections, but rather on the room for listening and recording of optimization, that is, for the recording of work to do optimal consideration.
(A)
Diffusion and its role
Diffusion on improvement of sound field and listening to interested has an important role, quadratic residue diffusion body because of its good diffusion capacity and convenient installation, now widely used. Quadratic residue diffusion of formula for hn = (λ 0/2 N)? ' Sn, Sn to n-squared divide by N remainder, λ 0 for diffusion center frequency wavelength, n is the number of diffusion of lattice (must be a prime number), h is the height of a lattice, n = 0, 1, 2, 3, 4, 5, 6 ....
Quadratic residue diffusion of diffusion frequency threshold approximately in the center of the lower frequency-doubling, limit depends on the number of squares, can reach the center frequency n-1 times.
Diffusion and smooth reflector, which can effectively avoid sound focus. When the sound wave through a smooth wall reflection, all of the sound energy is reflected along the same direction, its reflection direction fixed, depending on the location of the sound source. When sound waves through the diffusion of reflection, the sound energy is scattered reflection in different directions, and have different phase.
The formation of uniform energy of irregular reflection sound makes one ear subjective produces a sense of space, at the same time use in high frequency will improve the sound of the proliferation of "bright". Its reflection direction roughly a semicircle, sound energy average spread. Diffuser has another effect, when the sound source, the acoustic reflection through the back wall, if the reflector is a smooth wall, a band only fixed reflection path points to the location of the recording. But when the reflector is a diffuser, due to the proliferation of Sonic to semicircle direction, there are countless different band reflection path converges in the recording location, and so on, there are numerous points of convergence of the same nature, which translates into expanded the best listening to tempo.
(2)
Sound-absorbing material (structure) and its role
Sound absorption can be divided into two situations, low frequency and high frequency absorption and absorption. Sound absorption can reduce echo, but also can effectively control the reverberation time, improve listening to tempo frequency response also play a very important role. So, you can create a listen for more clear and more standard mix environment.
1. high frequency absorption
High-frequency absorption is mainly directed against sound field design, early reflection sound wave interference, reverb and ECHO's control. Usually you can use full-band sound-absorbing glassFibreboard for sound absorption and conducted jointly with the diffusion of sound shaping.
2. low frequency absorption (low frequency sound,)
(1) role
The role of low frequency sound, is to avoid low-frequency interference in wave and sound of the low frequency sound distortion. Shows, when za sound impact wall surface, after reflection of sound waves and za continue to issue of Sonic interference effects. Depending on the wavelength, the sound pressure or be strengthened or be offset, and different locations with different frequency response. In an untreated rooms, Sonic mutual effect of reversed phase interference occurs, most will produce 25dB even more.
Many people mistakenly believe that the use of near-field monitor speakers can exclude acoustic defect. In fact, as there will be a standing wave, just listening position to the sound energy is large. Although the human ear close to the speakers when, because of the high-frequency acoustic reflection will gradually decrease the masking effect, but the low-frequency interference still exists.
Another misconception is to use the equalizer to change because of acoustic phase cancellation caused by the change of frequency response. Sonic interference androom structure, is objective and existent, unless you change the direction of sound transmission, otherwise use equilibrium cannot be changed because the sound wave interference induced frequency distortion. And the different locations of the frequency response curve is totally different, so it is not possible to rely on the equalizer to compensate acoustic defect.
Although the use of headphones you can avoid the room acoustic problems caused by, but the headphones sound only direct sound, making it very difficult for us to go to control the volume of some tracks. When we use the headphones, the main play music or song in a very small volume, you can even listen to very clear, so our final mix, lead singer of the level will be slightly lower than the desired level of value. Similarly, reverb and delay also lack accurate judgment.
Without sound, treatment room, some frequencies decay time reached 300ms, this will give other low frequency tone produces a big impact, damage, or even make voice clarity is harmonious.
In General, a room need as many sound depression. Although he may make the room became the "dead", but the rooms can never have too many mixed low frequency. Sound, can be installed in a room corner, walls, floor and ceiling, the greater the processing area, ideal for low-frequency effects.
(3) commonly used in low-frequency sound
A. Hershey Helmholtz resonator
Helmut Helmholtz resonator and a low frequency sound, that is different from the composition of the sound of glass wool, it can absorb more low-frequency component. It has adjustable hollow structure, a band of absorption is very effective. Absorption frequency range and the quality factor Q, Helmut Helmholtz resonator cavity absorption bandwidth formula is: f2-f1 = fr/Q, fr for resonance frequency is the maximum absorption frequency. By adding glass wool or add several openings of different sizes, you can make the absorption band of variable width. Helmut Helmholtz resonator of many species, usually is uses a large box of internal fill glass wool, front end cover a series of different dimensions, different spacing veneer. This design is known as narrow plates resonator. Although the hull Helmholtz resonator can absorb a certain band, but it can absorb a limited range, and the use of multiple resonator frequency absorption of broadening its scope be on sound field of activity, so it must be very careful.
B. Panel sound,
Panel of the sound in a narrow band noise, which can absorb bandwidth for approximately a octaves, it can use a series of a square around the Panel sound, to cover the entire frequency, without having to use a very heavy materials to increase the acoustic range. Because of the low-frequency components are close to four octave, so you can pass a different thickness of the Panel of the sound absorption in a combination of different frequency of low frequency and high frequency components can be its Panel reflection, therefore install multiple Panel sound, nor will it makes sound absorption can be all too silent sound field caused. Front panel can also be other shapes or combination, if placed in the back wall can be up to the required role diffusion.
C. acoustic suspension of sound-absorbing structure
Due to the wide range of low-frequency radiation, energy intensity, so when the low frequency sound wave into suspension system, the suspension of affected with swing (Visual observation), so will its kinetic energy is converted to its kinetic energy and heat. And because the suspension of the angle is different, so the transmission of sound direction also changed, so that the equivalent of a voice of the labyrinth. Acoustic in which constantly crash and be absorbed up to eliminate almost all energy.
Acoustic design to achieve the following four objectives:
1.
Prevent standing wave and wave interference, and ensure the flat frequency response.
2.
Reduction of small resonant frequency of the room, even distribution of the sound field.
3.
Reduce large room reverberation time of low-frequency, the better the reverberation time frequency characteristics.
4.
By absorption or diffusion, prevent echo and improve stereo positioning capabilities.
5.
Sound needs to meet the requirements of control rooms.
Important factors to consider
1, early reflection
Initial delay gap refers to the direct sound and the first indoor reflection i.e. head early reflection of the time difference, as shown in the figure. In subjective listening to interested, initial delay gap will bring the room characteristics of perception. For example, when we are in a closed room darkness, applaud, we can know the approximate size of room. This is due to the perception of auditory system to its initial delay clearance and transmitted to the brain room information. When the initial delay clearance greater than 20ms, the room will have sense and produced open sound about the same 7m 20ms. Large control room of the side wall of the dots in the early reflection at least listening points 3-4 meters, so make sure you are on the side walls of absorbing or diffusion treatment.



Early reflections on listening quality have a critical role, rich early reflection can bring relative active sound field, and the appropriate early reflection to improve the clarity of the sound has a certain role. 50ms listening points within reach of early reflections will enhance the clarity of the sound, but the control room can not be too much to join their roomCharacteristics, so early reflection should try to control their energy. Selection of the diffuser is a good way to spread evenly, allowing early reflection enhance clarity and sound field with a certain sense of space. At the same time help to promote high-reflection, whereas the low frequencies loudness makes sound reflection, so non-roiling should only non-high-frequency components (center frequency is approximately 1kHz), reflection onthe low-frequency should be absorbed.
But early reflection will also bring comb filter, noise interference problems that affect the sound field of positioning and listening spot frequency response. Many people early reflections are very inconsistent, reflections on the direct sound serious interference, can affect the forward sound image orientation, and then it will be very dogmas and all of the reflex points all covered with absorption material, and to top the whole room filled with sound-absorbing materials! this will only be more attenuated sound energy that we in the mix is constantly upgrading and enhancing the reverb loudness.
We are in the control room as well as shrinkage concrete strip processing, you need a standard space environment, the band reverberation time and room of frequency response as straight. At the same time, we want to ensure that the reflection of sound does the formation of mutual interference or influence the comb filter frequency response.
2. room dimensions and shapes
Room structure to listen to the sound effects are:
Parallel walls of stationed in wave resonance problems
Asymmetric structure on the positioning of
(1) in wave and resonance
Standing wave is composed of two columns in the opposite direction, with the frequency of the sound wave overlapping. When parallel wall space is an integer multiple of half-wavelength, that is, standing wave generated axial. At the same time, there is a ramp and tangential standing wave. When standing wave continues, will have resonance. The room of the resonance frequency of the general formula is:



Where c is the speed of sound, lx, ly, lz-room length, width and height, n is 0, 1, 2, 3, 4, ….
When several resonance mode resonance frequency of the same, the phenomenon of resonance frequency degenerate. A degenerate resonance frequency on the same frequency and resonance of sound is greatly enhanced, this could cause serious distortion of frequency. In the low frequency range, this phenomenon is particularly serious.
(2) symmetric structure
Thanks to produce stereo positioning two speakers to the sound of the volume and the time is different, therefore, in order to ensure accurate positioning of the original signal, Binaural accept to room information to maintain a certain balance. That is, when the speaker plays a tone when the test signal, Binaural should accept to almost the same reflection sound signal. If the room is a rectangle, the speaker should call set in a relatively short length of the front end, making listening location away from the back wall, so that it can be avoided in the back wall, near the most complex sound interference. The following figure is a set of comparison chart, on the left is the correct symmetric structures, the right to not ideal layout structure. On the right, the left speaker's high frequency components can be directly reflected to the listening point, while the right side of the left part of the sound through speakers wall reflection, reflection through the back wall part, leading to listen and point on either side of the reflex sound different, resulting in the sound and image positioning offset.


4. measurement of acceptance
Standards are as follows:
(1) above Acoustics: 55dB
(2) the frequency of the reverberation time: T = 0.4s (125Hz? 4kHz allows +-0.1s error)
(3) listen to the tempo of the frequency response: no uniformity of control within the 3dB

【 Weak current College 】 fuse in the use of sound

On some needed to buy relatively expensive electronic limiter, you can try to use a standard AGC fuse to protect your speakers. AGC fuse those internal metal, ends with metal caps small glass tube. While electronic limiter is more advanced, it can "read" the content of an audio signal, the limiter of creation and the content of the signals in accordance with the need to protect the speakers. In comparison, the fuse is a relatively stupid devices. They are on the current and one fixed time constant response (for example: fast current or slow currents).
You need to do work
Here comes to fuse the hardware can very simply from RadioShack or other electronic components supply sources. You need to find the AGC fuse holder, fuse and take some artificial. A good AGC fuse holder should have that kind of block type. It's two "U"-shaped metal card and can be used to stuck in its previous fuse. There is another relatively slight narrowly AGC fuse holder that is an embedded with like pig tail-like wire retainer. This type of fixation is generally used in automobile aftermarket electronic component, you may be in the auto parts supplier found. The third option is that fixed on the back is equipped with a removable cap mosaic plate fixation, in many electronic devices can see such a fixation. They can be placed in the vast majority of Jack Panel, and makes all the connections are done internally. The capacity of its current capacity is perfectly fine. Any one can provide guitar amplifier stores will have this fixed.
AGC fuse often are more packed up together to sell, so naturally you "forced" into buying spare parts!
Installing fuse holder
The fuse holder installed in one convenient place. You can set the fixed installation in the speakers on the back of the input panel recessed, facing the back of the grid, the internal loudspeaker cabinet, or the location of the amplifier output. Remember, if a fuse is burnt, you must be able to easily replace one, but sometimes you need to act quickly (for example, in a performance of the process).
Regardless of the wire is to be received on or direct sound received Horn, fuse holder must press series welding. As for the end is the cathode or anode wire that is not important. Also, the fuse and it's fixed for there is no polarity. If you cannot use the welding method, then you should choose with conductor connection bolts embedded fixer, of course, this is not the best way.
Fuse in protecting what
Protection of an inner divider speakers the best approach is to fuse the divider in front of current insurance tube should follow each numerical sums for the Horn. This requires that the speakers are turned on and access to each of the speakers on the construction of the wire. If you choose to fuse holder on the outside of the box, then you may need to extend the speaker wires. You can wire up the holes from the body of a received either from the input panel wear out to you want to place the fuse holder in place. You must be this small hole closed to avoid wire around the air flow and leak. In this case you'd better be able to use the embedded form factors of holder, so that you can avoid the problem of sealing body and makes the skin more beautiful with speakers. Usually when you want to use a fiber gasket used to seal the hole is completed.
Of course for a multi-channel speaker system you can also use a signal insurance, to avoid for each loudspeaker installation of insurance work, however, such protection would not be so precise. For multilayer amplification system, you must have for every loudspeaker installed fuse.
Insurance choices
Now the only remaining problem is to choose what type and how much rated amperage fuse. If you are in for the entire system installed fuse, you should use fast current fuse. If you are a single horn installed fuse, it should be the treble (compression) drive select fast current fuse, tapered speaker select slow current fuse. This is because the drive than treble cone loudspeaker for instantaneous excessive current have a certain tolerance.
You have to calculate and to determine the energy ratio. RMS will give more protection, but may also be very easy to burn. If the audio content will not be very full bass, then you can safely use the ratio of energy, which is usually twice the RMS ratio.
You can use the following formula to calculate a numerical rating of insurance:
Amps = squareroot (watts/Ohms) (power/impedance after square)
For example: If a speaker (or speaker) of power is the 300 Watt (RMS or long power), the nominal impedance of 8 Ohms. Then
Amps=squareroot(300/8)
Amps=squareroot(37.5)
Amps=6.1
This numerical rating of insurance should be identified as 6 amps. Once the value of more than 3 amps, then you will be very difficult to find in a 1/4 amperes for the change of insurance, so you should use this number of recent fuse: use more than this number of fuse relatively less insurance, while the use of numerical base than this fuse is more conservative. If you want to install the entire system from the beginning, choose use speaker's RMS ratio. When you find that your insurance will be very easy to burn and you're sure you do not have excessive driving your system, you can swap the values higher than 1/2-amp fuse.
If you have a parallel in the two speakers, for example, two bass Horn, and when you want to use for both of them with a fuse, then you have to be represented by a single horn calculated rated insurance value doubled. If two Horn-line,Then use by a single horn calculated rated insurance value.

【 Weak current College 】 audio technology law and effect-14--Power By 【 China power house network 】

1. the frequency domain of subjective feeling

Frequency domain most important subjective feeling tone, like loudness as tone is also a kind of subjective mental capacity of the hearing, it is the level of hearing judge voice tone.

Psychology of tone and music scales is the difference between the former is a pure tone, while the latter is the music that combined the pitch of the voice. Composite sound tones not merely frequency resolution, is also the role of the auditory nervous system, listen, listen and experience and learning.

2. the time domain of subjective feeling

If the length of the sound over approximately 300ms, increase or decrease the length of time that the sound on auditory threshold change has no effect. For the pitch of the sound of feeling and the length of time. When sound duration is very short, did not recognize your voice, just hear "a la". Sound duration lengthen, you can have the tone of the feeling, only sound continuously for more than 10 MS, feeling tone to stability.

Time domain characteristics of another subjective feeling is echo.

3. spatial domain of the subjective feeling

Human ear ears listening than using single-ear listening has obvious advantages, its high sensitivity, listen to the valve, the sound source with a sense of direction, and has a strong anti-interference ability. In stereo, with speaker and stereo headphone listen and get a sense of space is not the same, the former sound seems to be located in the surrounding environment, and the latter hear sound position at the head of the Interior, in order to distinguish these two kinds of space, the former is referred to as directed, the latter is called localization.

4. hearing of Weber's law

Weber's law indicates that the person hearing the sound of the subjective experience and objective stimulation amount proportional to the logarithm of a. When the voice is small, increasing Sonic amplitude, the humanear's subjective experience increased a lot larger volume; when the sound intensity is greater, increasing the same Sonic amplitude, ear subjective experience significant increases of the volume is small.

According to the human ear in the listening, the volume control on the design circuit require exponential type potentiometers as volume control, so that uniform Rotary potentiometers turn handle, the volume is linear increase.

5. hearing of Ohm's law

Famous scientist ohm electrical was discovered, at the same time in the Ohm's law, he also discovered the human auditory Ohm's law, on the law of disclosure: ear hearing only the sound of all sounds in frequency and intensity, and the distinction between independent sound phase. According to this law, the sound system to record, replay, process control can not go to consider complex sounds in the min audio phase relationship.

Ear is a frequency Analyzer, you can convert the homophonic in tremolo, ear to frequency resolution sensitivity is high, at this point the ear than eyes high resolution, the human eye cannot see the white colour of light weight.

6. masking

Environment in other sound makes listening to a voice of listening, referred to as cloaking. When a sound intensity far louder than the other, when a certain level and that two sounds at the same time, people can only hear the sound of the voice and unnoticeable another sound exists. Masking and masking the sound of the sound pressure, masking the sound of the sound pressure level increases, the amount of increase as cloaking. In addition, the low-frequency sound masking range is greater than the range of high frequency sound masking.

Ear of the auditory characteristics to design reduce noise circuits provide important insights. Tape playback, so the listening experience, when the music and sounds in continuous change is large, we will not hear the noise floor of tape, when the music ends (blank section of the tape), it can feel to tape the "' ..." noise exists.

In order to reduce the noise impact on program sound, signal to noise ratio (SN) concept, which requires that the signal strength than the noise intensity enough big, so listen would not have felt the presence of noise. Some of the noise reduction system is the use of masking effect of the principle of design.

7. dual ear effect

Binaural effect principle is this: If sound comes from listening to the front, as the sound source to the left and right ear, so the same distance from the left and right ear sound waves reach the time difference (phase), tone difference is zero, you feel that the sound comes from listening to the front, and not biased towards one side. Sound intensity, you can feel the noise source and listen to.

8. Haas effect

Test proves: Harris in two sound sources at the same time, the sound, a sound source with another sound source of delay quantity, binaural listening experience is different and can be divided into the following three scenarios to illustrate:
(1) two sound sources in a sound source with another sound source of delay amount within 5 ~ 35mS as if the two sound sources into one, listen and can only feel ahead of the existence of a sound source and direction, not another sound source.
(2) If a sound source delay another sound source 30 ~ 50mS, already feel two acoustic source exist, but the direction is set by the leading.
(3) If an amount greater than the sound source delay another sound source is 50mS, you can feel the two sound sources at the same time, direction of individual sound sources to determine the latency is clear and echo.
Haas effect is stereo system one directional basis.

9. de? wave El effect

De? wave El effect is stereo system directed another Foundation. De? wave El effect is: placed left and right channel two speakers, listen to two speaker symmetric line listen and give two speakers-infeed different signal,you can get the following findings:
(1) If you give two speakers into the same signal, that is, the intensity levelPoor Δ L = 0, t = 0 Δ time difference, you only feel a sound, and from two speakers on the line of symmetry.
(2) if the only speaker of intensity differentials Δ L is not 0, you listen and feel the sound preference more loud a sound box, if the intensity differentials Δ L is greater than or equal to 15dB, feel the sound entirely from a sound that only speakers.
(3) if the intensity differentials Δ L = 0, but the time difference of the two speakers Δ t is not 0, you feel the sound to be reached by the speaker orientation. If the time difference is greater than or equal to Δ t 3ms, feel sound entirely from first arrived only speaker orientation.

10. Lloyd's effect

Lloyd's effect is a stereo range of psycho-acoustic effects. Lloyd's effect revealed: If the delay of signal then RP superimposed on direct-to-signal, will produce a clear sense of space, the sound seems to come from all directions, listen to it in the band.

11. Keyhole effect

Mono recording system using a microphone recording signals in a track, all the way to the amplifier is used for playback and a speaker, the sound source is a point source, like listening to through the door of the keyhole to listen to the Interior of the Symphony, this is the so-called Keyhole effect.

12. bathroom effect

Confront the bathroom there is a personal feel and the sound in the bathroom, the reverberation time is too long and too much, this phenomenon in the electroacoustic technology sound effect called bathroom in the description. When a low, intermediate frequency, resonance, exaggeration of the frequency response is flat, 300Hz lifting excess, bathroom effect.

13. the Doppler effect

Doppler effect reveals mobile sound for listening features: when the sound source and listen to the relative motion between, will feel a frequency determined by thesound of his voice changed when the sound source to listen who approached is frequency at a slightly higher pitched, when the sound source left is slightly lower tone frequency. The frequency of change called Doppler frequency shift. Closer to the sound source in listening to the same distance than does not move when the intensity is high, and remove the source of strength to smaller, often sound source to the direction of movement.

14. likai test

Likai test proves: two sound sources in phase contrast, sound like you can out of two sound sources, or even jump to listen.

Likai test also prompts, as long as proper control of two sound sources (left and right channel speakers) intensity, phase, you can access a wide range (rotation, depth) of the mobile field.

【 Weak current College 】 car audio noise removal method

When using a car audio or replace the audio, the audio will produce more noise, noise can affect the sound quality, the lower the audio indicator, or even the entire sound system cannot listen for noise issues, the introduction of noise sources and basic troubleshooting.
First, the source of noise
Noise from the following channels into car audio system.
1, invade the power cord (through the host and the amplifier power cord into the system).
2, through the Earth's current (via xxx ground and power amplifier of the ground).
3. subject to other wire harness induction (via xxx receive and original car harness induction).
4. electrical interference (electric Horn, motors, etc.).
1, 2, 3, there is a correlation.
2. meet noise countermeasures
Generally deal with the noise-to-use components, automotive capacitor or coaxial motor capacitors (particularly effective to deal with high-frequency noise), Earl flow ring (ICP), LC filters, grounding, diodes, etc.
1, against ignition system noise
Check ignition coil cathode on the capacitor is installed, such as installation check capacity is reduced, if size reduces Platinum-contact easily spark erosion, interference, you need to replace the electrical capacity of 0, 5UF/400V promise of capacitance.
Check ignition voltage is using carbon fine line, if you use wire-prone to interference, which is a radio interference, so the parts must be replaced.
You can increase the damping resistance, noise suppression sparks by 1 megohm resistance concatenated output main high-voltage ignition coils, reduce interference.
2, the motor noise removal
First audio equipment and signal cable from the motor and motor line, available 1 only promise of capacitor in parallel at both ends of the motor, you can also only with 2-line in motor inductor respectively and cathode ray, then 2-polarity motor Capacitor respectively in the positive and negative cables, on the other side of the Earth form filtercircuit that spark of absorbing carbon brushes so that the noise reduction.
3, no relays electric Horn noise, exclude method has the following main categories:
In one of the speaker terminals on the ground and then a capacitor.
-In one of the Horn of a Terminal first-line to ground inductance, and received a capacitor.
In the two speaker terminals on the use of method-respectively.
In the steering wheel of the loudspeaker button-contact a capacitor between parallel.
4, the relay electric Horn noise, exclude method has the following main categories:
Electric Horn bracket and body should contact good.
-In relay contacts at both ends, a capacitor in parallel, or in contact with both ends of a capacitor in parallel.
? Use 3,? and ˉ method.
5 grounding bad will produce noise.
If the hood failed to secure the entire earth, bonnet becomes a xxx, the car noise radiation produced by ministries to the surrounding space and from xxx and the circuit into the audio system. Bonnet and body equipped with a connector, required to land on paint, grease, dirt, etc. are completely eliminated.
Engines (engines) and the body, or between front wheel suspension, body, between exhaust pipe and the body should have a good connection.
6. power cable noise suppression:
To effectively eliminate power line noise, should put Earl flow ring * near power amplifier installed. If there is a lot of power amplifiers, each power amplifier is installed near a stream circle because Earl noise from a power amplifier to another, so that a single failure of Earl flow ring.
7, to the signal cable (RCA) incoming noise suppression:
Signal cable should be located away from power cables and power cables are installed on both sides of the body, so that you can avoid the possibility of interference. The signal cable is double shielded network, you should put the outer shielding network attached to the chassis.
In practice also encounter many problems, but the important thing is to find the source of interference, then the remedy to solve it, so that the car audio system for playback of each program are clear and pure perfection.
Noise is the car audio fault because most and more difficult to troubleshoot because the vehicle's structure and lines of more complex, easy to place a lot of noise, so you should have some auto circuit and car audio knowledge, troubleshooting can be handy.
Solution: first of all, according to the noise analysis and judgement by principle identify failure is part of, and then take different exclusion method.
Simple exclusion approach, first listen to the audio of the radio, tape and CD part are the noise, if you have to check the power cord, Earth wire, signal line, the alignment of the parts is reasonable, the signal line whether with or without loosing ground breaking the skin, the power amplifier should be insulated with the body. In response to different noise sources, take different measures for processing, if the noise cannot be excluded, is to generate noise signal source disposed before the measures taken against noise, so that we can resolve the noise.

【 Weak current College 】 how to properly use VHF and UHF wireless microphone

Wireless microphone because there is no transfer cable, easy to use, flexible and widely used. But if improper selection, often occur with intermittent, sound choppy signal, noise, sound quality is poor and not far from the transmission distance, produce, such as the main reason is not based on field and use the correct selection of wireless radiation of wavelengths and the correct method of installation.
The widespread adoption of wireless microphones VHF (very high frequency) and UHF (ultra-high frequency) two transmission frequency band. VHF-band range 30MHz?? 300MHz, wavelength for 10m?? 1m, usually called "metric". UHF-band frequency range is 300MHz?? 3000MHz, wavelength for 1m?? 0.1m, commonly referred to as "decimeter". Both radio frequency is widely used for TV, FM radio, mobile phones, pagers, stock information machines, microwave communications and radar, etc. Channel extremely crowded.
A variety of radio wave propagation in the space of freedom, time and geographical constraints, frequency overlapping intersections, without constraints and regulations inevitably produce interactive, the world's radio waves using a uniform requirements, so that the interaction between them is minimal. Wireless microphone allowing use of the frequency range of requirements:
VHF frequency band for 169MHz?? Total occupancy 230MHz 61MHz frequency range, and 6-12 TV channels of the same frequency range. In 61MHz frequency range is divided into A, B, C three segments, namely: (A) for the VHF 169MHz?? 185MHz, VHF (B) for 185MHz?? 200MHz, VHF (C) to 200MHz.
UHF frequency band to 690MHz?? Total occupancy 960MHz 270MHz frequency range, and TV 35?? 68 channels can be set to the same extent as the hundreds of wireless microphone channels. If necessary, the frequency range you can also scale up, set more wireless radio channels.
VHF and UHF two band characteristics of radio wave propagation
VHF and UHF radio frequency signals of collectively (RF), but the UHF bandmaking greater use of direct radiation of electromagnetic waves, VHF band except the use of direct radiation of electromagnetic waves, the used part and diffraction of electromagnetic energy, therefore in the same transmitter power and transmission, the transmission distance can be further. The reason for this is:
(1) metal objects on electromagnetic wave propagation and reflection of the barrier
Metal objects on electromagnetic wave has a barrier and reflection effects. Barrier effect of electromagnetic waves emitted wavelength and the size of the metal objects. Electromagnetic waves of a wavelength less than the size of the metal objects, you will be subject to reflection, electromagnetic wave propagation. That is the higher the frequency, metal objects, the stronger the reflection of electromagnetic waves. If electromagnetic waves of a wavelength greater than the size of the metal objects, electromagnetic wave will bypass the metal barriers continue to spread (diffraction). Obviously UHF VHF of reflectance reflex more stronger.
(2) electromagnetic wave on the metal grid (or perforated metal plate) penetration capacity
Electromagnetic waves of a wavelength greater than metal hole distance between the grid, the diffraction of electromagnetic waves will pass, the lower the frequency, the longer wavelength longer wavelength, through the more metal grid.
(3) non-metallic body (such as the human body and walls) on the role of electromagnetic wave absorption
The higher the frequency of the electromagnetic wave, non-metallic body, the greater its absorption, electromagnetic wave propagation loss.
(4) the air temperature on the influence of electromagnetic wave propagation
The higher the frequency, the greater the electromagnetic wave propagation loss. Propagation loss is also proportional to the size of the humidity.
Wireless microphone signal quality and transmission distance
Wireless microphone signal quality directly affects the transmission distance. Signal quality (S/N) and transmit power and space field strength distribution, receivers and receiving antennas for quality, efficiency and outside interference sources is closely related to the situation.
(1) to solve the electromagnetic field intensity fluctuation of measures
Because indoor objects reflection and absorption of electromagnetic wave propagation in multiple ways, so that the space of the electromagnetic wave field strength promulgated very complex, some parts of the field strength is weak, some parts of the rendering area of the "shadow", or even become a corner. When the transmitter and receiving antenna distances frequently change, the undulation of the field is changed. When receiving antenna in a weak field locations, the "mute sound" points or poor sound quality. To do this, the wireless microphone receiver with dual antenna diversity reception technique (Diversity) and AGC AGC technology to give up. Diversity reception technique is set in a receiver with two sets of identical reception antennas and two receivers and one through built-in computer chip circuit automatically detects and automatically choose a stronger way to receive the signal as the received signal, in collaboration with AGC control, you can effectively resolve the "mute sound" point.
Unfortunately the market a lot of cheap fake double antenna wireless microphone receiver, these counterfeit products in addition to the two receive antenna, there are no diversity reception device, so you cannot solve the problem of the "mute sound".
(2) wireless microphone transmitter power
Increase transmit power to increase the transmission range for wireless microphones. But wireless microphone transmitter power from radio wave effects on the human body, power supply voltage of the battery life and interference to nearby devices, and other factors, market products are limited to transmitting power 2mW?? 50mW。 Due to technical reasons, of VHF frequency band of transmitting power than UHF transmitting power easier to do it, the price is cheaper.
(3), receive antenna
, Receive antenna type, length, and match status directly affect the antenna gain and efficiency. Efficient, receive antennas are 1/2 wavelength omnidirectional radiation dipole antenna (half-wave dipole antenna). If the length of the antenna and the wavelength is disproportionate, will directly affect the transmission distance. UHF of short wavelength, so the UHF antenna VHF antenna with than a shorter length, transmitter antenna easier to install.
(4) interference signal
Interference signal increases wirelessMicrophone output will make noise, serious wireless microphone does a for. Interference signals from industry interference, TV and radio signal interference and wireless microphone between adjacent channel interference and other radio frequency interference, etc.
Industry interference: including automobile ignition systems, radio and cleaners, glow discharge lamps (fluorescent lights, neon lights, high pressure mercury lamp). The majority of their interference in the VHF frequency band of spectrum.
TV, FM radio, information and mobile communications platform, transmit power, frequency range, VHF band interference is greater than on the UHF band interference. The solution is to first find the interference source frequency range, and then select use avoid these frequency wireless microphone channel.
More wireless microphone between adjacent channel interference: in many wireless microphone use, often encounter adjacent channel at the same time, if one channel of harmonics fall into another channel occurs adjacent channel interference, the solution is to choose to use a frequency interval of channels. VHF band can choose the number of channels, the UHF band can choose many intervals larger channel.
How to choose?
In the above two band wireless microphone performance compare, VHF-band wireless microphone advantages of 1?? 8 point disadvantage is: 9?? UHF-band 16 points; wireless microphone has the following advantages: 9?? 16 points, the drawback is: 1?? 8 point. Selection should be based on the use of occasions and their characteristics, the "strength", give full play to their greatest strengths.
In General, suitable for VHF hotels, Convention Center, Sports Hall (Hall), function rooms and teaching system suitable for radio and television; UHF, theatre performances and demanding, many group channel at the same time work wireless microphone system. But regardless of which band, choose dual antenna diversity reception technique of high-performance receiver will have better results and more clear sound. If you need to increase the transmission distance, the receiving antenna mounted to close off the transmitter, and (or) use the antenna amplifiers, not blind pursuit of increased transmitter power.