Decibel Comparison Chart taken from hearnet.com

[Suppressor Professor]

http://www.hearnet.com/at_risk/risk_trivia.shtml

• Decibel (Loudness) Comparison Chart
  Environmental Noise
  weakest sound heard 0 dB
  normal conversation at 3-5 ft 60-70 dB
  dial tone of telephone 80 dB
  city traffic inside car 85 dB
  1983 OSHA monitoring requirements begin 90 dB
  
  train whistle at 500 ft. 90 dB
  subway train at 200 ft. 95 dB
  regular sustained exposure may cause permanent damage 90-95 dB
  power mower 107 dB
  power saw 110 dB
  Pain begins 125 dB
  
  pneumatic riveter at 4 ft. 125 dB
  jet engine at 100 ft. 140 dB
  loudest sound that can occur 194 dB
  
  Musical Noise
  normal piano practice 60-70 dB
  fortissimo singer 3 ft. away 70 dB
  chamber music in small auditorium 75-85 dB
  regular sustained exposure may cause permanent damage 90-95 dB
  piano fortissimo 92-95 dB
  violin 84-103 dB
  cello 82-92 dB
  oboe 90-94 dB
  flute 85-111 dB
  piccolo 95-112 dB
  clarinet 92-103 dB
  french horn 90-106 dB
  trombone 85-114 dB
  timpani & bass drum rolls 106 dB
  average Walkman on 5/10 setting 94 dB
  symphonic music peak 120-137 dB
  amplified rock music at 4-6 ft. 120 dB
  rock music peak 150 dB
  
  
  NOTES:
  
  The brass section playing fortissimo can drown out practically the whole orchestra.
  One-third of the total power of a 75-piece orchestra comes from the bass drum.
  High frequency sounds of 2-4,000 Hz are the most damaging. The uppermost octave of the piccolo is 2,048-4,096 Hz.
  Aging causes gradual hearing loss, mostly in the high frequencies.
  Speech reception is not seriously impaired until there is about 30 dB loss; by that time severe damage may have occured.
  Hypertension and various psychological difficulties can be related to noise exposure.
  The incidence of hearing loss in classical musicians has been estimated at 4-43%, in rock musicians 13-30%.
  Statistics for the Decibel (Loudness) Comparison Chart were taken from a study by Marshall Chasin , M.Sc., Aud(C), FAAA, Centre for Human Performance & Health, Ontario, Canada. There were some conflicting readings and, in many cases, authors did not specify at what distance the readings were taken or what the musician was actually playing. In general, when there were several readings, the higher one was chosen.

[court1984]

• ...loudest sound that can occur 194 dB...

That's not entirely true, just for anybody that might repeat that statement.

[wolf]

• ...loudest sound that can occur 194 dB...

That's not entirely true, just for anybody that might repeat that statement.

Tell us

[cocoboots]

Theoretically, the max is 194ish for audible sounds

[BigDave@SMDW,LLC]

Since a dB is a ratio of the loudest versus the quietest, I will pull some info from HamRadio that I know.....

In ham radio, it is all about power output of the antenna. You cant be heard if the power doesnt get out.....

hams use the term effective radiated power and measure it in dBs since it is a universal measurement. (Ratio)

3 dB is the same as 2 x the original value
6 dB is 4x
10 dB is 10x (this is the only place this occurs)
20 db is 100x
30 dB is 1000x
40 dB is 10,000 x the base value

So if 40 dB is 10,000 times the base value, I can only imagine what 194dB would be. I know that in ham radio that the guys who do moon-bounce will build antennas with 250dB of gain and more if they can.

If your can measures in a 124dB and your buddies can clocks in at 127dB, then in theory his can is twice as loud as yours. If I am understanding this right.

Dave

[cocoboots]

sound is vibrating waves that travels trough air, gases, matter..etc. generally, we associate sound with our auditory sense only. However, we also sense low frequency and high amplitude vibrations (sound) though our tactile sense. for example, a large firework's "boom" has a large amplitude that we hear because it occurs at a frequency that our auditory system can process (it's not infrasonic nor ultrasonic) and we also feel the "boom" (large amplitude) as pressure. when we discuss the amplitude of a wave we characterize it by it's pressure on the surrounding environment. because we can hear such a wide array of amplitudes a logarithmic scale is used so that very high and very low pressures can be compared more conveniently. so, we say that a can has a suppressed level of 24dB instead of saying it has a suppression of 1x10^24 Pa.

to determine the theoretical limit of sound in earths atmosphere we need to use the equation for sound pressure.

Lp= 20 log (P1/P0) where Lp is the sound pressure level, P1 will be the sound pressure in our atmosphere and P0 is the reference sound pressure. the reference sound is .00002 Pa (Pa=pascal-unit of pressure) This is the amplitude of the quietest sound we can hear. P1 is 1 atmosphere because that is our standard atmospheric pressure. 1 atm is a pressure of 101325 Pa.

So:
Lp = 20 log (101325 Pa/ .00002 Pa) = 194 dB for audible ranges

[hemi]

Lp= 20 log (P1/P0) where Lp is the sound pressure level, P1 will be the sound pressure in our atmosphere and P0 is the reference sound pressure. the reference sound is .00002 Pa (Pa=pascal-unit of pressure) This is the amplitude of the quietest sound we can hear. P1 is 1 atmosphere because that is our standard atmospheric pressure. 1 atm is a pressure of 101325 Pa.

So:
Lp = 20 log (101325 Pa/ .00002 Pa) = 194 dB for audible ranges

Ooh yeah, that makes it easier to understand

[Conqueror]

Since a dB is a ratio of the loudest versus the quietest, I will pull some info from HamRadio that I know.....

In ham radio, it is all about power output of the antenna. You cant be heard if the power doesnt get out.....

hams use the term effective radiated power and measure it in dBs since it is a universal measurement. (Ratio)

3 dB is the same as 2 x the original value
6 dB is 4x
10 dB is 10x (this is the only place this occurs)
20 db is 100x
30 dB is 1000x
40 dB is 10,000 x the base value

So if 40 dB is 10,000 times the base value, I can only imagine what 194dB would be. I know that in ham radio that the guys who do moon-bounce will build antennas with 250dB of gain and more if they can.

If your can measures in a 124dB and your buddies can clocks in at 127dB, then in theory his can is twice as loud as yours. If I am understanding this right.

Dave

Power is not the same as volume. Human perception of volume ("loudness") is based on amplitude rather than frequency or power. Decibels are actually a measure of power, not volume - essentially a measure of the force of oscillation of the air molecules carried by the propagating sound wave, if I remember my physics right. While the two are related - higher amplitude yields higher power) they are not the same thing. You can have a very POWERFUL sound wave - which wil meter HIGH Decibels - but if its frequency is only 100Hz most humans will not describe it as a loud sound.

This is why dB readings on silencers are only half the story. You also see people describing "tone" - two different cans can have identical dB ratings but produce sounds of different frequencies, resulting in completely different sounds.

[Suputin]

Explosions can reach 220+ dB and we can hear them.

[cocoboots]

just because an apparatus measures an explosion at 220 dB does that mean you hear 220 db? of course you would have your sound meter set to mil-spec...

[Suputin]

One of the problems with "hearing" very loud events is that the pressure wave can travel through the skull and impact the auditory nerve and hearing structures of the ear from inside. Is this "hearing" the sound? Maybe, maybe not but it can certainly damage the hearing.

[cocoboots]

nuclear explosions would be louder than 220dB, but probably destroy all testing apparatus...and life.

the space shuttle launch is loudest sound event that is regularly repeated. it ranges between 210-200 dB. the sound can still be measured 300+ miles away and 20+ min. after the shuttle launches. at 220dB and .02Hz the sound would be infrasonic, so you're correct that it would pass through us and impact the auditory nerve.

are you an engineer, educator..etc?

[Conqueror]

Remember, dB is not a measure of VOLUME, it is a measure of POWER. There are points at which a longitudinal pressure wave is no longer a SOUND wave, but a SHOCK wave. An explosion will meter very high on the dB scale because it produces a very strong wave of compressed air - like a sound wave on steroids. But a shock wave is not "audible" so it cannot be called a loud "sound". While it is of similar construction to a sound wave, it cannot be heard. It is the sound equivalent of UV light - not perceptible by human organs, but nonetheless present and quantifiable.

[pneumagger]

Good EM anaolgy CQ. The biggest thing to remember when using dB to quantify a sound you hear is that it is indeed logrithmic. For example, although 6dB is indeed 2x the power os 3dB, 20dB is not twice as loud as 10dB... 20dB is 10x louder than 10dB!

below is a visual depiction of a logarithmic scale. The X (left-to-right) axis is equally metered while the Y (bottom-to-top) axis is logarithmically scaled. Some of you with yardage focusing rings on your scope's objective lense may recognize the unbalanced metering as seen here



-When the world throws you for a curve, hit it with a log to straighten it out.

[cocoboots]

But a shock wave is not "audible" so it cannot be called a loud "sound".

in my example, i meant louder to mean larger in value. sorry i didn't use the correct verbage, i was just getting home for the night. as i noted later in the post, the wave is approx .02 Hz and it wouldn't be audible

[Suputin]

are you an engineer, educator..etc?

Phffft. No. I am just a student of silencers and by association the sound silencers are trying to dampen.

But a shock wave is not "audible" so it cannot be called a loud "sound". While it is of similar construction to a sound wave, it cannot be heard.

I'd dispute that notion that only those things we can hear can be classed as "sound". Dogs hear ultrasonic noise that we can't. Does that mean what dogs can clearly hear is not sound just because we can' hear it? The term ultrasonic clearly has the word root "sonic" in it which means this is sound we are talking about.

It is the sound equivalent of UV light - not perceptible by human organs, but nonetheless present and quantifiable.

And the fact you note that UV is still a form of light (although not percieved by our eyes) kind of backs up my point above.

I realize we are straying into the philosophical a bit here but I think that in the case of compression waves travelling through the atmosphere, it is all sound regardless of wether we can hear it or not.

[renegade]

dB is a logarithmic unit of measurement that expresses the difference in magnitude of a physical quantity. When used for sound, it usually means Sound Pressure Level. In other words, it is a ratio of two different SPLs.

[renegade]

nuclear explosions would be louder than 220dB, but probably destroy all testing apparatus...and life.

the space shuttle launch is loudest sound event that is regularly repeated. it ranges between 210-200 dB. the sound can still be measured 300+ miles away and 20+ min. after the shuttle launches. at 220dB and .02Hz the sound would be infrasonic, so you're correct that it would pass through us and impact the auditory nerve.

are you an engineer, educator..etc?

I think the Shuttle is around 180, which is the peak a few seconds after liftoff. It is louder after liftoff because there is a ground based sound suppression system. Inside the cockpit is the low 140s.

I have been as far as 20 miles away and heard it.

[PeteSB]

Remember, dB is not a measure of VOLUME, it is a measure of POWER. There are points at which a longitudinal pressure wave is no longer a SOUND wave, but a SHOCK wave. An explosion will meter very high on the dB scale because it produces a very strong wave of compressed air - like a sound wave on steroids. But a shock wave is not "audible" so it cannot be called a loud "sound". While it is of similar construction to a sound wave, it cannot be heard. It is the sound equivalent of UV light - not perceptible by human organs, but nonetheless present and quantifiable.

I hear you, no need to shout. LOL
JK
Pete

[BookHound]

Thanks for posting that, Cara. Interesting stuff.

Mark