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And pull their mouth away when they hit stronger notes. Mics can only take so much sound pressure. Every mic is different too. As I stated above, there are many variables to account for to even remotely have a chance to use sound to measure velocity. It would have to be in an extremely controlled environment with calibrated sound and metering devices. In addition, the swing must be absolutely repeatable as would the contact.  There is no possible way to use the dB meter on my iPhone to accomplish this. It’s not rational to think you could. It’s not even that good at measuring the sound level of my amps accurately. Even reorienting it by 45 degrees changes the level.

I know there are a lot of people on the site with science and engineering backgrounds here so @p1n9183 is getting a lot of questions about how this theory would even work, but I’m going to ask the obvious one here… why? Like what is the purpose if you already have a speed radar, even if such a thing as you proposed was feasible?

It might be at some distances, but none are realistic. For example, if I put a microphone 2.5m away from a sound source and another 3.5m away, the fall-off there is only about 3 (2.98 I think), but your sound would have to be incredibly loud. A microphone that picks up an 80 dB sound at 1 millimeter will only pick up about 12 dB at 2.5 meters (and it's still only 20 dB at 1m from an 80 dB sound source). I also don't think swinging a club generates a very loud sound, and sounds that can injure your hearing require 85 dB or so. In other words… You need to generate (at the source) an ear-injuring level of sound with your club, and if the microphone is as little as one foot away, that 85 dB is already down to ~43.5 dB. It's almost half of what it was. Swing 14" away with the same 85 dB swing instead of 12" and the same swing will read 42 dB. Sound attenuation is subject to similar laws like light fall-off because it radiates, so it diminishes in the inverse square: I have also talked to some sound engineers, and they've laughed and said that unless you were controlling EVERY aspect of this, including: temperature distance of max clubhead speed from the microphone angle (both axes) to the microphone clubface orientation (a face open or closed will change the frequency) location of the max clubhead speed (reaching peak speed at the same exact place) everything in the vicinity, including the shoes and clothes you're wearing, the surface you're on, etc. ideally with all of them producing virtually no noise even when moving. You'd have to control all of those to within very small margins. Even just the doppler effect is going to dramatically change your input. No. No, you need to realize how wrong you've gotten all of this. See above about the doppler effect. Unless you're a swing robot, you're not going to generate the max speed at the same exact location every time. Tell me, @p1n9183, why do you think recording artists (singers) put their mouths so damn close to the microphone?

Digging deeper... you can use the frequency of the woosh also.  It is possible to measure the speed of an object using the noise it generates when passing through a decibel reader,  but with some limitations and considerations. The method relies on the relationship between the frequency of the sound emitted by the moving object and its speed.  When an object moves at a constant speed, it generates sound with a characteristic frequency, known as the "Doppler frequency." The frequency of the sound emitted by the object can be related to its speed using the formula: f = (v / c) * f0 where: - f: frequency of the emitted sound - v: object speed - 😄 speed of sound (approximately 343 m/s in air at standard temperature and pressure) - f0: frequency of the sound emitted when the object is at rest Having "C" been constant, and "f0" been unknown but equal for both swings you only need to compare the frequency of  each swing to know how much faster or slower is a swing over the other.  

As I told you before, the sound attenuation is 3 db at 1 meter (38").  At 7" (your example) is a wooping 1 db less, for an 80db 7 iron is under 1% error. I know for sure that my PRGR is not that accurate, even my skytrak isn't that accurate. For a FREE unit seams to be promising if you can't afford a speed meter.   Again, you are swinging in the same spot, over and over again in the same session. Phone position is the same , background sound is the same, environment is the same. The only difference is the peak sound you produce when you whoosh the club.     You need to do a lot better to discharge an idea.