Air Rifle Sound Analysis
Posted: Sun Dec 29, 2013 9:21 pm
First, I need to thank IFGian Basu for giving me this idea.
I have a disclaimer to make: This kind of "study" can hardly be described as "scientific". It is more of a "timepass" study.
Basuda and I exchanged a few emails where he wondered if the internal events in an air rifle could be recognized from the sound picture. I decided to approach the question in the following manner. I made 3 sound recordings:
1. The sound of a normal air rifle (SDB 50) shooting
2. I suppressed/muffled the sound from the muzzle by burying the muzzle in a thick wad of cotton wool and then recorded the sound
3. I suppressed/muffled the sound from the receiver by wrapping the receiver and barrel in a thick blanket and recording the muzzle sound only after that.
I put the sound signatures of the three shots together in a sound editor and analysed and compared them.
Here is a screen grab of the three sounds that I analysed as displayed in Audacity sound editing software
Comments:
Theoretically, it is expected that the first sound from an air rifle should be the sound of release of sear, followed by the sliding of spring. After that one should hear the pellet exiting followed by the bang of the piston hitting the end of the chamber. All this time there will be the twang of the spring and sounds of various frequencies produced by vibration of the air rifle.
I discovered that the sound of the normal air rifle and the sound of the receiver alone (no muzzle sound) are very very similar in length and frequency. The sound of muzzle alone is much shorter duration and of lower frequency.
The receiver sound and full air rifle sound lasted nearly 0.25 sec. The only difference was that the full rifle sounds had peaks from 1500 Hz to 5000 Hz (high). The receiver sounds were mainly high pitched (5000 Hz). Muzzle sounds were very short in duration (just 0.12 sec) and low frequency with peaks at 1000 Hz.
When I sub analysed each sound I found that the earlier parts of the "full air rifle" sounds had lower frequencies and the later parts had the higher frequencies. But I was not able to say that the lower frequencies were specifically caused by the muzzle.
However in an earlier thread ("Physics of springers") I had calculated that the pellet is out of the rifle within about 0.05 seconds from pulling the trigger. On the other hand the receiver sounds and vibration last 5 times as long. It seems to me that the sound of the pellet coming out of the muzzle, which is both of low volume and low frequency is simply buried within all the other sounds and it is impossible to look at the sound signature and find the exact point at which the pellet emerges.
Just my conclusion...
I have a disclaimer to make: This kind of "study" can hardly be described as "scientific". It is more of a "timepass" study.
Basuda and I exchanged a few emails where he wondered if the internal events in an air rifle could be recognized from the sound picture. I decided to approach the question in the following manner. I made 3 sound recordings:
1. The sound of a normal air rifle (SDB 50) shooting
2. I suppressed/muffled the sound from the muzzle by burying the muzzle in a thick wad of cotton wool and then recorded the sound
3. I suppressed/muffled the sound from the receiver by wrapping the receiver and barrel in a thick blanket and recording the muzzle sound only after that.
I put the sound signatures of the three shots together in a sound editor and analysed and compared them.
Here is a screen grab of the three sounds that I analysed as displayed in Audacity sound editing software
Comments:
Theoretically, it is expected that the first sound from an air rifle should be the sound of release of sear, followed by the sliding of spring. After that one should hear the pellet exiting followed by the bang of the piston hitting the end of the chamber. All this time there will be the twang of the spring and sounds of various frequencies produced by vibration of the air rifle.
I discovered that the sound of the normal air rifle and the sound of the receiver alone (no muzzle sound) are very very similar in length and frequency. The sound of muzzle alone is much shorter duration and of lower frequency.
The receiver sound and full air rifle sound lasted nearly 0.25 sec. The only difference was that the full rifle sounds had peaks from 1500 Hz to 5000 Hz (high). The receiver sounds were mainly high pitched (5000 Hz). Muzzle sounds were very short in duration (just 0.12 sec) and low frequency with peaks at 1000 Hz.
When I sub analysed each sound I found that the earlier parts of the "full air rifle" sounds had lower frequencies and the later parts had the higher frequencies. But I was not able to say that the lower frequencies were specifically caused by the muzzle.
However in an earlier thread ("Physics of springers") I had calculated that the pellet is out of the rifle within about 0.05 seconds from pulling the trigger. On the other hand the receiver sounds and vibration last 5 times as long. It seems to me that the sound of the pellet coming out of the muzzle, which is both of low volume and low frequency is simply buried within all the other sounds and it is impossible to look at the sound signature and find the exact point at which the pellet emerges.
Just my conclusion...
to your efforts....