dB A measurement logging

[Saroor]

Hi I am using Umik-1 with REW for application. My application is basically to measure the sound from a machine assembly. For that I have tried to use SPL funcntion and logger data from there. But I would like to minus of my ambient (surrounding) sounds and get only final sound from the machine assembly itself. Is there any way to do that.?

 

[jschwender]

UMIK mikes are onmidirectional, a directional microphone would pick up sound only from the direction you point it to.

 

[DanDan]

Izotrope RX can probably reduce it. There may be other De Verb software. But why? Why not take a LAeq of the Ambient while the machinery is off and simply subtract?

 

[John Mulcahy]

If the ambient is more than 15 dB lower it will make less than 0.1 dB difference. Make sure the subtraction is done correctly.

 

[DanDan]

If the ambient is more than 15 dB lower it will make less than 0.1 dB difference. Make sure the subtraction is done correctly.

Indeed, no harm to remind ourselves that dB Arithmetic is different, and nice little calculator in that link tx. Differences can be different though... Contributing a 30dB LAeq background noice to a 45dB LAeq will indeed go unnoticed. But vice versa will raise the noise level by close to 15dB. So it is IMO legitimate and common in the context of Noise Control to use simple linear subtraction to describe the change in level, i.e. the difference. Perhaps also reminding ourselves that LAeq is a figure averaged over time from samples which might be quite diverse. e.g. a passing car.