# Decibels of Bow



## JParanee (Oct 13, 2009)

It's not scientific by any means but it showed me what it needed to know


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## Bender (Dec 6, 2006)

I've done it. Actually got a couple of articles on the subject of bow noise published in TBM.

Your readings seem kind of loud when you look at a chart like seen here:
http://www.noisehelp.com/noise-level-chart.html

HOWEVER

Using a decibel meter can be tricky. How close is the meter to the bow? Are you shooting inside or outside? How close is the target? Sometimes, depending on target material, impact can be louder than the bow itself. This can over ride the signal you're actually looking for. Heck even walking back and forth to shoot and then check the meter can over ride your signal. Its helpful to use 2 people, one to shoot and one to run the meter and record results Is your meter digital with a MIN/MAX or Peak Hold function? 

Set up outside, with your meter say about 10 feet from the shooter, with another person to monitor the meter, and set your target (Really its just there to catch the arrows) WAAAAYYY down range and I bet you'll get significantly different, lower, readings.


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## MGF (Oct 27, 2012)

If I were serious about measuring bow noise, I would use a spectrum analyzer or an O-scope. That would let me isolate the part I was interested in...ie ignore target impact and baseline ambient "noise". You could also mount an accelerometer to the bow and directly measure vibration displacement and frequency, although, that wouldn't translate directly to perceived sound.

All that said, I'm not sure why I would bother. LOL my bows seem to shoot pretty quiet IF I shoot them well.


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## dan in mi (Dec 17, 2009)

MGF said:


> If I were serious about measuring bow noise, I would use a spectrum analyzer or an O-scope. That would let me isolate the part I was interested in...ie ignore target impact and baseline ambient "noise". You could also mount an accelerometer to the bow and directly measure vibration displacement and frequency, although, that wouldn't translate directly to perceived sound.
> 
> All that said, I'm not sure why I would bother. LOL my bows seem to shoot pretty quiet IF I shoot them well.


This ^ plus frequency.


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## Still mustang (Jan 22, 2014)

My testing is not scientific by any means. I can say that last night I made some Wool Puff balls for my Red Wing. 30 wraps at 3.5". This made a big difference to the ear but not so much to the Decibel App on my IPhone. They did appear to make a difference to the speed of the bow, POI of impact about 2-3 inches lower at 25yrds. 
I'm not sure what differences can be made when shooting at Whitetails. At 10-15 yrds I'm not sure a deer could move fast enough to alter POI enough to matter. At 15+ I think that yes they can but can you get a bow quiet enough to matter?
I hunt mostly on the ground and I think that matters to but I don't know that.


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## BarneySlayer (Feb 28, 2009)

If you want to measure sound level with an SPL meter...

Use the 'A' weighting, this filters out the less audible frequencies, in a gradual manner, so that the meter reads something in proportion to actual perceived loudness.

Use the 'Fast' setting.

Shoot in an area where you've got nothing to reflect sound in the immediate area.

Put the meter on a tripod, at a fixed, consistent distance from the bow, I'd suggest about 2 meters (just because sound measurements are usually done in meters. Loudpseakers are often spec'd at 1 or 2 meters. 1 meter for sensitivity, and often measured at 2 meters for frequency response, giving enough distance to let all of the drivers align).

Measure the bow sound in multiple directions (i.e., in front of you, behind you, to the side, and maybe even at 45 degree increments in between. If you can measure directly above and below, as well as right next to your head, even better.

If you _really_ want to know, do all of the above, recorded, and analyze with an FFT waterfall plot, showing the sound distribution of amplitude versus frequency versus time. I don't have the equipment for this, and I haven't had the motivation to do the first part, but I keep meaning to


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## Aronnax (Nov 7, 2013)

BarneySlayer said:


> If you want to measure sound level with an SPL meter...
> 
> Use the 'A' weighting, this filters out the less audible frequencies, in a gradual manner, so that the meter reads something in proportion to actual perceived loudness.
> 
> ...


That's all fine with keeping things scientific, but isn't the only thing that matters is what the deer hears? Why not place the db meter at some "normal hunting distance" directly out in front of the bow?

BM


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## Fury90flier (Jun 27, 2012)

because that's not how measuring SPL is done.


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## martha j (May 11, 2009)

you can never get it quiet enough for a deer.


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## DDSHOOTER (Aug 22, 2005)

Martha is right, so why try?
Dan


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## Fury90flier (Jun 27, 2012)

because today's generation, for some reason, don't understand history.


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## BarneySlayer (Feb 28, 2009)

Given the option, I'd prefer the bow to be quieter, just because.



> That's all fine with keeping things scientific, but isn't the only thing that matters is what the deer hears? Why not place the db meter at some "normal hunting distance" directly out in front of the bow?


To me it's not the only thing that matters, but I get your point. Even so to do so, you'd have to agree on 'normal hunting distance', and once you did that, something more relevant, the location of the shooter and the deer.

The farther you get from the sound source, in an echoic environment (meaning it's not anechoic, it has real objects that reflect sound, as opposed to a room with acoustic foam and fiberglass wedges), the more of the sound that you hear has been reflected, as opposed to traveling through the air without any reflection (direct.) You always hear the direct sound first, but unless there's a substantial delay between the initial arrival of the direct sound and the first arrivals of the reflected sounds (and the reflected sound will be smeared over time, as different paths of reflection are different distances), you don't hear them separately. Your ears may use this information to determine direction of origin, in part, but you really can't distinguish which is louder, explicitly at least.

Because so much of the sound you hear will be reflected, the amplitude of it will depend highly on what was between (and around) you (the microphone) and the source (the bow).

And, because the bow is a pretty complex radiator, how loud one bow is versus another may possibly depend on where it is. I haven't tested this extensively, of course. This is purely commenting on something of interest.

But, consider that a recurve bow has limbs that will be working as dipolar radiators (back and front surfaces will be radiating out of phase). The middle of the limbs, between the string contact points at resting, may also flex in opposite motion from the tips of the bows, on the other side of the string contact points at resting. What's more, the radiating surface is curved, so that the direction the limbs are facing will affect the dispersion of the sound. It also varies in width, such that the directional dispersion will vary as a function of frequency. You then also have the sound to be considered by the string itself, which will be moving in all manner of directions perpendicular to the up/down axis. If you combine all of this, keeping in mind that every sound wave, traveling any given direction, will either constructively or destructively interfere with every other sound wave being generated, you can imagine that the whole thing is a mess, and that the sound that a bow makes, how loud it is, the frequency distribution, depends a lot on direction and distance.

So, I think you're right, in that if you really want to know what a bow will do in any given specific instance, you should simply measure it in that instance. However, if you're looking for testing results that can be applied generally, i'd lean towards figuring out what the bow does, in general, and then make your best guess on what you think might happen from there.

Or, settle for subjective personal experience, do what you like, and don't worry about it because A), as it has been pointed out, it's unlikely that you're going to be shooting a bow, at hunting distances, that a deer _can't_ hear, B), from a hunting standpoint, you don't really care what a deer can hear, but rather what will make a deer move before your arrow gets there, and C), what one deer does or does not react to isn't a predictor, necessarily, of what another deer will do or not do.

Still, it's fun to talk about


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## DDSHOOTER (Aug 22, 2005)

Don't forget the VHF and UHF that you can't hear but maybe damaging to the bow itself. That should be more concerning. Alike a dryfire. Lol. 90 dBm is very high. So high that you maybe in violate of your city ordinance? Lol.
Dan


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## Still mustang (Jan 22, 2014)

I don't think my IPhone App very accurate. I appreciate all of the responses. I intend to remove some wool yarn before the next time I shoot. Try going from 30 to 25, see what difference that makes.


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## Thin Man (Feb 18, 2012)

Barney,

"Dipolar radiators"? Yer durned tootin'!

A sound engineer told me an interesting story about a very famous rock band (yes, this absolutely relates to archery if you read on!). This is a very true story. Their guitarist (who shall remain nameless here to preserve the legend) was having trouble hearing himself sing during concerts in spite of the tremendous vocal volume of his own voice aimed directly into each ear from dual monitors eight feet in front of him. He asked his sound engineer to solve the problem. 

During the next night's sound check, the sound engineer stood with the guitarist on stage to analyze the problem. The band played, and the engineer noted (and this is why a good sound engineer makes the big bucks!) that the guitar player's amp, which was directly behind the player, was so unearthly loud that it was completely masking the unearthly loud vocal monitors. 

_"Why don't you turn down the guitar amp ... there's a mic on it and I'll boost it up for the house."
"No ... I like it loud ... this is rock and roll."_

Since you don't argue with a guitar hero's wisdom, the sound engineer thunk and thunk. After a few seconds (yes, this was a hot-shot engineer) he said, "Let me grab your backup amp from backstage and give me a few minutes to rig something up that might help."

Okay, so now we end up with two fire-breathing, unearthly loud amps behind the guitar player. How can doubling the fire power behind the guitarist, which should make hearing his voice all the more difficult, possibly solve the problem?

Ah ... but there's a twist! The sound engineer triangulated the amps behind the player, with each amp's sound axis intersecting the exact spot where the guitarist stood when he sung. He then adjusted one amp's speakers to be out of phase with the other amp's speakers. In other words, one amp would push positive as the other pulled negative. No biggie, for both sound exactly the same. But ... if you are standing in just the right place (at the singing mic), the massive sound of the each amp is radically reduced due to the phase cancellation of positive and negative waves intersecting at that precise point. 

The band played the song again. When the guitarist stood at the mic, he could now clearly hear his own voice through the monitors due to the extreme (and uncanny) reduction of guitar volume at that spot. When he backed out of the spot to do the requisite heroic pose and play a solo, his ears bled even more ever due to the blistering, dual titans behind him, both with every dial twisted all the way up to "10". From that night on, the sound engineer would always adjust the amps in this manner, and use tape to place an "X" on the stage where the guitarist should stand when he sang.

And the guitarist was happier than ever!

The moral of the story is:

If the bow's sound is an issue, hunt with a buddy. Each archer should triangulate at an equal distance from the game, and each take a shot at the game at exactly the same moment (assuming you have tuned your bows to be out of phase with each other). If not tuned out of phase, you merely need to calculate the millimeter difference between each archer's distance from the game to achieve a "manual" phase differential by offsetting each others limb/string compressions and rarefactions. You could also accomplish the same thing by offsetting each shot by a predetermined micro-second whilst standing at the exact same distance from the game. Personal preference and team strategy will be the determining factors here, for all of these methods will serve well to accomplish the same result.

The game won't hear a thing!

(One day I'll relate the story of a well-known singer in the pop vein who simply refused to stay put on the very important piece of tape that his sound engineer indicated would allow him to hear his voice as well as his band. He'd wander the stage while singing, become angry when he couldn't hear himself, and fired multiple engineers throughout the tour, blaming each of them them for his problems hearing himself on stage ... and all this after they had shown him the hot-spots, marked them with tape, and he had agreed during the sound check that all was well for the show!)


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## Fury90flier (Jun 27, 2012)

inverse sound? I remember some studies NASA did about that...maybe it was the Army. It was testing done about quieting turbine engines where they used transducers to replicate the sound but 180 out...the results were impressive. Wouldn't be too difficult to create a transducer to make the opposite sound of your bow.


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## BarneySlayer (Feb 28, 2009)

Fury90flier said:


> inverse sound? I remember some studies NASA did about that...maybe it was the Army. It was testing done about quieting turbine engines where they used transducers to replicate the sound but 180 out...the results were impressive. Wouldn't be too difficult to create a transducer to make the opposite sound of your bow.


I think you're onto something...

Record your bow at the target location (where you've got the apple dangling from a fishing hook, trying to catch salmon), put a wireless transceiver and motion switch in the arrow, to sense release, have the playback/transducer device, with inverted polarity near you (Or if you want it closer, you can have it digitally delay. Heck, you could even build in a range finder to both your bow and the playback device, and have to adjust delay accordingly.

Get a guy with a bushy beard to vouch for it on a hunting show.

Have JP handle the business end of it...

We're gonna make millions!

Cool story SKinny!


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## DDSHOOTER (Aug 22, 2005)

Thin Man said:


> Barney,
> 
> "Dipolar radiators"? Yer durned tootin'!
> 
> ...


Cool story about phase lock loop amps.
A simple fix would be to wire the opposing speckers reverse polarity. Meaning out of phase. When specker are arranged facing forward you wire them in phase. So if two archers shot at the deer facing each other that would cancel but would be very dangerest.
Dan


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## Still mustang (Jan 22, 2014)

This is a great idea! Now I need someone to go hunt with me. Volunteers shouldn't be hard to find with such great ideas. It will be dangerest but we wont need speckers...


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