whisper decibel readings

sorry this took so long guys.

as I said when I first got my whisper ( http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=6567&mid=46758#M46758 ), I wanted to make a dB comparison to my crosman 2100 classic pump.

first a quick disclaimer, I am a musician of twenty years (a drummer). I have soundproofed a few rooms in this time, and chose the longest room in my house with "some" dead ability (isolation of pellet stop noise, no "bouncy" walls). Sound variations WILL be different if you choose to buy a good meter and perform the same test, unless you have the same room measurements and same obstructions.

obstructions are anything a sound wave can bounce off: walls, a couch, etc. also it does matter how many openings you have in your room also, where the sound can escape.

here is the room I used:



the stick in the lower part is the rifle, and the roomis 11' wide and about 30' from tip of the rifle to the pellet trap face.

I used crosman premier hollow points in both rifles, 10 pumps on the crosman.

all measurements are taken in the same Z axis (this is VERY important). distance from B to C (Y distance) is approximately 19'.

each rifle got 5 shots for each location, and I have posted the averages of each rifle in each location.

I used a high quality (expensive)  industrial OSHA approved dB meter I have had for some years. it records over a given time, and gives you the high and low points. in effect, each shot I took was also "averaged" out over its split second time duration, given its peak dB rating.

*please note this is a new gamo whisper, maybe fifty or so shots through it before the test, whereas the crosman is a seasoned rifle, about a year old, with 108 tree rat kills under its belt.

locations are marked for reference to the following numbers.

A: (trigger action)
whisper: 80.5 dB
2100: 77.6 dB

B: (five + feet left of muzzle)
whisper: 67.8 dB
crosman: 76.6 dB

C: (far left)
whisper: 66.3 dB
crosman: 75.4 dB

D: (far right)
whisper: 63.0 dB
crosman: 76.8 dB

E: (five feet + right of muzzle)
whisper: 60.4 dB
crosman: 78.0 dB

hopefully this information will be useful to everyone.
any questions, feel free to ask!

-Mark

[SGTMEATSAUCE]

Thanks for all the effort. As best as I can read, the Whisper is a bit quieter..

[CharlieDaTuna]

Because the two guns have totally different power plants and the one not being a springer, what is presented is reasonable and somewhat expected. What would be really interesting is the comparison of say a Shadow or even the Hunter series (with about the same velocities) to the Whisper. Kinda like apples to apples. I would expect the Hunters to be a bit louder though because of the wood stocks with little absorbtion. Maybe I have that backwards.   Your thoughts Mark... Can you pull it off?? I think we would really like to see that.

I'd like to do that Charlie, and I agree with you, but I only own one springer to my name.

I know the test is not a true A to A comparison of power plants, I wasn't trying for that anyway. I just wanted some real decibel numbers. I stuck in my crosman just for fun, comparing it to what I already had. I am glad I did spend the money on the whisper now.

I do find it interesting that the lower powered rifle was actually louder than the more powerful springer (advertised 755 vs. 1000). I assumed the higher power would make more noise and with most rifles I have been around over the years.

are pumps normally louder than springers? I didn't think they were, but I could be wrong. I still consider myself very new to these.

my next test would be after a pro tune up, just to see how much twang is reduced............but that would be subjective truthfully because it would might be changing the pitch, not necessarally the dB amount, making it quieter to the human ear but still having some oomph in the dB range. So, that test might not work.

either way, this post might be a good reference to people that are particular like me and want solid data numbers. I couldn't find whisper dB ratings ANYWHERE when I went looking before I wanted to buy.

-Mark

Your sound levels at the trigger were very similar to mine but levels away from the action were different.  I tested the RWS 48, Gamo Big Cat and the Gamo Whisper.

Trigger levels:
The RWS: -87.29 db
The Whisper: -88.98 db

Muzzle Levels taken 3 foot in front and 1 foot to the right:
The RWS: -34.75 db
The Big Cat: -36.00 db
The Whisper: -48.16db

The thing I noticed the most was the duration of the sound:

The RWS:   Sound Duration   
   0.075   secs
   0.07   secs
   0.072   secs
AVG Duration   0.072 secs

The Whisper:   Sound Duration   
   0.148   secs
   0.136   secs
   0.129   secs
AVG Duration   0.138 secs


The RWS had a tight high sound whereas the Whisper had a lower pitched sound that simply lasted twice as long but was a good bit quieter from the muzzle.

yep. thats what happens when you try to "deaden" or "supress" a soundwave.

"bouncing" the sound (as inside of the supressor) makes the wave longer, and lower in pitch, making it quieter to the human ear.

your not actually getting rid of it, your just changing it into another form. Soundproofing a room doesn't really get rid of the sound wave, it just transfers the vibration into heat that gets absorbed into the material.

I think your measurements were of *threshold* shift, right? that would explain why your numbers came out different. my comparison was striaght dB numbers.

edit: also remember, the room where you test plays a big difference with wall bounce. Also, you were using a mic (a 58 or 57? I forget which) whereas I was using a dB meter. a mic has a larger cone of where the sound will be picked up. I used to use the same model live on my snare drum.

-Mark