Application to measure frequency ?

Hi.
Is there an application for an Android phone you may suggest that can tell by sound the frequency Hz (cycles per second) of a noise ? Would like to find the RPS (Hertz) or RPM (multiplying by 60) of an air compressor.
Seen several applications listed but none convincing; seem more automotive oriented, with selection of 4,6,8 cylinders, 2, 4 strokes...

I’ve wondered that myself that would be very helpful for experiments with resonance!

Could probably whip something up with a arduino

There are many "guitar tuner" type apps, that will display the frequency of a tone.
The limitation may be the low frequency response of the phone mic..

This one for Android is decent.



Keep in mind with machinery vibration (and therefore airborne noise) that there will be tones at more than shaft rate (rotation rate).

Some examples:

0.4–0.5× excessive clearance in sleeve bearings
1× balance and/or alignment
2× alignment

Non‐integer peaks between ~1× – ~10× rolling element bearing deterioration

Forcing frequencies – number of elements such as:

Fan blades
Pump impeller blades
Motor rotor bars
Gear teeth

× rotation speed


Reciprocating machines with have many strong harmonics of shaft rate.