Sound Barrier?????

KnotRight

KnotRight

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Two questions:

Does it make a difference at what speed you break the sound barrier? 1200 ft/sec vs 3000 ft/sec

Does it matter the size of the object breaking the sound barrier? 40 grn bullet vs a 147 grn bullet
 
I think mass and speed are both variables to the loudness of the BOOM or CRACK.... they only reason I say so is that the other day, I read about USAF working on a quiet Mach jet that should minimize the sound over populated areas.
 
KnotRight said:
Two questions:

Does it make a difference at what speed you break the sound barrier? 1200 ft/sec vs 3000 ft/sec

Does it matter the size of the object breaking the sound barrier? 40 grn bullet vs a 147 grn bullet
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From what I’ve read:
1)- concerning noise, no
2)- a subsonic 40g bullet isn’t quite as loud as a 400g 45/70. They’re both pretty quiet.
 
Michael458 said:
Actually a good question, I don't have a definitive answer to. It would not be a big issue to find out for sure however, Decibel Meters are not very expensive, I am looking at one on Amazon now for $22.90.
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Pretty sure those on amazon as well as apps on our phone are inaccurate as they are often either not designed for the Db levels we see with firearms and/or aren’t sensitive enough to catch the momentary spikes. This is why we see those who test suppressors using $5k+ Milspec/ISO meters.
The cheap ones and phone apps are fun, just not very accurate from what I’ve read.
 
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The ballistic crack is the same, as in anything traveling supersonic will creat one,
However, a 22LR/9mm, fired through a good suppressor will sound quite different than a 50BMG fires through an efficient suppressor,
Basically, the heavier/faster projectile holds the note longer
 
Jerzsubbie said:
Pretty sure those on amazon as well as apps on our phone are inaccurate as they are often either not designed for the Db levels we see with firearms and/or aren’t sensitive enough to catch the momentary spikes. This is why we see those who test suppressors using $5k+ Milspec/ISO meters.
The cheap ones and phone apps are fun, just not very accurate from what I’ve read.
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Could be, not my area of expertise............
 
Spartan01 said:
this is absolutely true.

so many factors play into this-

temperature
Humidity
Altitude
Speed
Caliber
Shape
Efficiency of suppression
Wet or dry tech
Piston, gas, or bolt
Distance projectile is allowed to travel (big one)
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The only things that would change would be:
if I load a 9 mm at speeds of 1100 and 1150 ft/sec, what is the difference I would hear. And then if I load 308 168 grn bullet at 2600 ft/sec and a 40 grn 204 Ruger at the same speed will I hear a difference?
Same day, all shots fired within 5 minutes.
 
KnotRight said:
The only things that would change would be:
if I load a 9 mm at speeds of 1100 and 1150 ft/sec, what is the difference I would hear. And then if I load 308 168 grn bullet at 2600 ft/sec and a 40 grn 204 Ruger at the same speed will I hear a difference?
Same day, all shots fired within 5 minutes.
Click to expand...
Not bullets, but may be relevant:

As the size and weight of the aircraft increases, the intensity of the sonic increases. This is because a larger aircraft displaces more air, and a heavier aircraft needs a greater force of lift to sustain flight. Thus creating a louder and stronger sonic boom.

https://aviation.stackexchange.com/questions/2560/do-bigger-aircraft-make-a-bigger-sonic-boom
 
Mike V said:
Not bullets, but may be relevant:

As the size and weight of the aircraft increases, the intensity of the sonic increases. This is because a larger aircraft displaces more air, and a heavier aircraft needs a greater force of lift to sustain flight. Thus creating a louder and stronger sonic boom.

https://aviation.stackexchange.com/questions/2560/do-bigger-aircraft-make-a-bigger-sonic-boom
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The physics is the same, the larger bullet will create a louder sonic crack. The difference isn’t linear though and I don’t know how to calculate it, we need a fluid dynamics guy.
 
Exactly it’s exponential in its progression.

dB are a weird metric.
Every 3dB is roughy double what it previously was.
However, the way sound pressure levels work is measured in watts.
200 watts is twice as loud as 100 watts, however, because the progression is geometric and not linear, it would take 1000 watts to sound twice as loud as 100 watts
 
KnotRight said:
The only things that would change would be:
if I load a 9 mm at speeds of 1100 and 1150 ft/sec, what is the difference I would hear. And then if I load 308 168 grn bullet at 2600 ft/sec and a 40 grn 204 Ruger at the same speed will I hear a difference?
Same day, all shots fired within 5 minutes.
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I don’t know if there’s a difference in 2000fps vs 3000fps...but there could absolutely be a difference in 1100 & 1150. In addition to subsonic and supersonic, you have an area in between called transonic. You may have some actually become supersonic, or if it stays in the transonic range it will be louder than true subs.

0FEE5ECC-D453-4213-9325-4FA79DA2C8BD.png
 
And no, any app you try or affordable (to most) sound meter isn’t going to be accurate. They’re not fast enough to catch the peak of a gunshot. There’s actually only 2-3 on the market that are certified to handle it.

The one Silencer Shop uses for all their videos doesn’t give accurate data.

A lot of them would be good for sustained noises, like a rock concert or construction site, but they aren’t able to accurately capture the fast rise and fall times of a gunshot.
 
Also,
You need to measure at the barrel,
Then a few feet later, after the gunshot itself has died off, and measure just the bullet,
Additionally, you need to factor in the ejection port gas escaping, and mechanical noise of the firearm.
 
Spartan01 said:
Exactly it’s exponential in its progression.

dB are a weird metric.
Every 3dB is roughy double what it previously was.
However, the way sound pressure levels work is measured in watts.
200 watts is twice as loud as 100 watts, however, because the progression is geometric and not linear, it would take 1000 watts to sound twice as loud as 100 watts
Click to expand...

On wattage: I am a Luddite here, and only know anything of this coming from guitar tube amplifiers.
But my understanding is that 100 watts is NOT twice as loud as 50 watts.
100 is twice as loud as 10watts.
50 watts will be closer to 80% as loud as 100 watts.
Is this not true?

Having heard all 3 in same room it sure seems that way. 50 will clear the room almost as fast as 100!
 
BigWaylon said:
I don’t know if there’s a difference in 2000fps vs 3000fps...but there could absolutely be a difference in 1100 & 1150. In addition to subsonic and supersonic, you have an area in between called transonic. You may have some actually become supersonic, or if it stays in the transonic range it will be louder than true subs.

View attachment 176572
Click to expand...

Also bullets can create shockwaves that become supersonic themselves even if the round itself is not. Saw a neat video on that recently
 
Spartan01 said:
Exactly it’s exponential in its progression.

dB are a weird metric.
Every 3dB is roughy double what it previously was.
However, the way sound pressure levels work is measured in watts.
200 watts is twice as loud as 100 watts, however, because the progression is geometric and not linear, it would take 1000 watts to sound twice as loud as 100 watts
Click to expand...
This type of scale is sometimes referred to as a logarithmic scale. The scale for measuring intensity is the decibel scale. The threshold of hearing is assigned a sound level of 0 decibels (abbreviated 0 dB); this sound corresponds to an intensity of 1*10-12 W/m2
 
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