Audio and Acoustical FACTSThings you should know for better understanding of Church SoundThese terms are in no particular order.

1. dB (Decibel) - a term used to describe sound pressure level.

2. An increase of 3dB in sound pressure level is twice the power.

3. When you double the distance from a given point, the sound level decreases 6dB. *

4. RT60 is the time it takes for a sound such as a balloon burst to decay 60 Decibels.

5. A 60 Decibel increase is equal to increasing the power 1,000,000 times.

6. To hear a 1dB change in sound, you need to be in a recording studio or similar room.

7. To double the (perceived) loudness of sound, you need to double the power 3 times, or 9dB.* Another way to describe it is to say 10 times the power. If 10 watts = 70dB at 50 ft, you will need 100 watts for 80dB at 50 ft. To increase the level to 90dB you will need 1000 watts of power. (Most round off to10dB difference to describe doubling the loudness. It does make it easier to plan a sound system that way.)

8. Sound travels at 1130 feet per second.9. To know the length of a sound wave you divide the Frequency by

the Speed of sound. (100 hertz divided by 1130 equals 11.3 ft.)10. The tone of a sound is called "frequency".11. The wavelength of 80Hz (the low end of a

persons voice) is 14.06 feet.12. To create a sound, an object has to vibrate a

full cycle of movement which involves a push and pull motion.

13. 3dB - the smallest amount of sound pressure change average people can hear.

14. A decrease of 3dB in sound pressure level is cutting the power in half.

15. When you half the distance from a given point, the sound level increases 6dB.*

16. Frequency is "vibrations per second", which in

turn is called "Hertz" (Hz)17. The human voice has both fundamental

vibrations and harmonic vibrations.18. The Energy or Fundamentals of the human

voice has a range of 80Hz to 1200Hz. .19. Harmonics extend the range of the human

voice up to 6,000Hz.20. Harmonics are multiple vibrations of the

fundamentals.21. Harmonics are what make each voice and

instrument different sounding.22. ESSS sounds in speech are often caused by the

spaces in a person's teeth.23. For a surface to control a frequency, it has to

be as thick as 1/4 the wavelength. (Carpet 3/4-inch thick with 1/2-inch underpad begins to absorb sound above 2,000Hz.)

24. Building acoustical control into a church when it's being built often doesn't cost the church anything extra except for the knowledge of how to do it.

25. Sound travels through water faster than through the air.

26. Sound travels faster as humidity increases.27. ESSS sounds are from 5,000Hz to 9,000Hz.28. The wavelength of 2,000Hz is 6.75 inches.29. The wavelength of 200Hz is 5.63 feet..30. Carpet absorbs sound above the speech range,

making carpet a poor controller of speech in a large room. This also kills the musical aspect of the room.

31. What is not absorbed by a surface (like carpet) is reflected back into the room.

32. Opening a door changes the bass response of a room. The more doors are opened, the greater the change.

33. The terms MLSSA, TEF, TEF-20, SMAART, EASERA.... all refer to test equipment or software or both for measuring all aspects of church sound and acoustics.

34. NC = Noise Criteria - a standard that suggests the allowable amount of noise by frequency.

35. The Bible has a very specific plan for church

sound.

36. The Bible has a specific plan for Sanctuary design that is as current today as it was 2000 years ago.