There are many myths and misconceptions that people have about room acoustics.  Many aspects of acoustics are counterintuitive.  Here’s a quick sampling of fast facts about room acoustics.

1. dB (Decibel) is a term used to describe sound pressure level.
2. An increase of 3dB in sound pressure level requires twice the power.  Likewise, a drop of 3dB cuts the sound power in half.
3. 3dB is the smallest amount of sound pressure change normal people can discern.
4. RT60 (aka “reverberation time”) is the time it takes for a stopped sound to decay 60 Decibels.
5. A 60 Decibel increase is equal to increasing the power 1,000,000 times.
6. To perceive a 1dB change in sound, you need to be in a very quiet environment such as a recording studio.
7. To double the (perceived) loudness of sound, you need to double the power 3 times, or 9dB.
8.  Sound generally travels through the air at 1,127 feet per second at room temperature.
9.  Sound travels faster at high temperatures, and slower in cold environments.
10. Sound travels over 10 times faster through a pine wood wall stud than in air.
11. Sound travels more than 4 times slower through SilentWrap and SilentImpact than in air.
12.  Frequency = vibrations per second.  The official term for frequency is Hertz (“Hz”).
13.  The frequency range of human hearing is from 20 Hz to 20,000 Hz.  The high-frequency range of hearing is reduced with aging.  This loss is accelerated by excessive exposure to noise.
14.  The human voice contains both fundamental vibrations (which define “pitch”) and harmonic vibrations (which create the recognizable timbre of a given voice).
15.  The fundamental frequency range of the human voice is 80 Hz to 1,200 Hz.
16.  However, Harmonics extend voice frequency content up to 6,000 Hz.
17.  Harmonics are multiples of fundamental frequencies.  “Middle C” on a piano is about 262 Hz, but this sound also contains information at 524, 786, 1,048, 1,310 Hz etc.
18.  Harmonics are what make each voice and instrument “sound” different.  Without harmonics, a clarinet, a trumpet, and a saxophone playing the same notes would all sound the same.
19.  “SSS” sounds in speech are often caused by air moving between the spaces in a person’s teeth.
20.  “SSS” sounds range from 5,000Hz to 9,000Hz.
21. The wavelength of 2,000Hz is 6.75 inches.
22.  The wavelength of 200 Hz is 5.64 feet.
23.  The wavelength of 20 Hz is over 56 feet!.
24.  Carpet absorbs sound primarily above the speech range, making carpet a poor controller of speech or music in a large room.  Excessive absorption at high frequencies also kills the musical character of a space.
25.  What is not absorbed by a surface (like carpet) is reflected back into the room.
26.  Building acoustical control into a church, auditorium, or any other listening space when it’s being constructed often doesn’t cost much extra.  It’s largely a matter of knowledge on how to do it.
27.  It always costs more to fix an acoustic problem after-the-fact.

To learn more about why the speed of sound is different for various materials, please click here.