【 Weak current College 】 reproducing common knowledge

1. known speaker sensitivity 90dB/w/m, 1W power, 8m Office sound pressure level to 72dB

2. known speaker sensitivity 72dB/w/m, plus 64w power, 1m Office sound pressure level to 90dB

3. known acoustic signal of frequency f = 50HZ, its cycle for 0.02s

4. known acoustic signal of frequency f = 50HZ, its wavelength is 6.8m

5. known as the acoustic signal wavelength, its frequency to 0.34m 1KHZ

6. known acoustic signal wavelength for the cycle to 0.001s 0.34m.

7. enter a voltage amplifier output 100mV, 100V, its voltage gain is 60 DB

8. enter a attenuator 2V output when the voltage gain 1V is-6 DB

9. a power amplifier input 100mW output 10W, when its power is 20 DB gain

10. the characteristics of a divider to-6dB/oct represents the octaves attenuation 6 DB

11. a filter characteristics-6dB/dec represents ten octaves attenuation 6 DB

12. one rated power 100W, 8 Ω-amplifier, 4 Ω speaker system, output power about 200W

13. a rated power 100W, 8 Ω-amplifier, received 16 Ω speaker system, output power about 50W

14. three voltage gain of 100 times the voltage amplifier gain, total thread as 120dB

15. the three power gain is 100 times the power amplifier is threaded, total gain to 60dB

16. the three voltage attenuation is 10: 1 attenuator thread, total attenuation-60dB

17. an amplifier output voltage 0dBu, equal to 0.775 Volt

18. an amplifier output voltage 20dBu, equal to 7.75 Volt

19. an amplifier output voltage-20dBu equals 0.0775 Volt

20. the amplifier output power of formula equals (output voltage) 2/load impedance

21. amplifier the signal noise ratio of formula equals 20lg (output signal voltage/noise voltage)

22. amplifier received 8 Ω load measured output voltage of 8V, 8W output power to the amplifier

23. the amplifier output signal voltage 10V, noise voltage to 100mV, its signal to noise ratio is 40dB

24. the speaker 1m Department of sound pressure level is 110dB, away from the speakers at the direct 8m acoustic sound pressure level is 92 DB

25. the speaker sound pressure level at 1m is 110dB, distance to the speaker's direct-to-2m acoustic sound pressure level is 104 DB

26. sound is the sound pressure level at 1m is 110dB, then from the speakers at the direct 4m acoustic sound pressure level is 98 DB

27. language and music both auditoria system level 2 specification requirements 0.125-4kHz of acoustic gain to ≥-12dB

28. requests from the speakers at the direct 16m acoustic sound pressure level is, in the distance 84dB speaker 1m Department direct sound field sound pressure level is 108 DB

29. velocity C = 340m/s wavelength λ =, Sonic, Sonic frequency f = 0.034m 10KHz

30. velocity C = 340m/s wavelength λ =, Sonic, Sonic frequency f = 0.068m 5KHz

31. a speaker whose rating sensitivity to 93dB/m/w, now give it with 100W power, the speaker of the sound pressure level 1m Department should be 113 DB