# How to get the frequency/hz of a give audio signal?

Anyone know how to get the frequency/hertz of a given audio signal?

I’ve been trying to find a way to do it in audacity (with the analyze functions) but have been unable to thus far.

The hz signals I’m trying to figure out will be in the 30,000 to 60,000 hz range (lol)

Those are not audio signals. “Audio” by definition refers to sound, and as anything above 20kHz is inaudible to humans…

Signals in the 30-60kHz range require a sample rate greater than 120kHz. Does your sound card support this?

No, my soundcard only goes up to 20 khz I believe. However, I have a method to double it that gets me up to 40 khz.

I need to find out what khz any specific remote control operates on. To do this, I’d just point the RC at this ‘device’, bypassing a computer (if possible). Most remote controls operate at 38khz, but some go lower, some go higher - the method I’m using can’t emulate remote controls that go higher than 40 khz though, thus the need for testing to see what RC’s it’s possible on.

Sounds like it might not be easily doable though, since it’s unlikely anyone else has had to do something like this.

Edit: Found one!

That’s more or less what I’m looking for. Think I’ll just try to build one of those (or maybe just buy it)

You could scale down the frequency by 10 by using a decade counter to make the ultrasonic audible …

Frequency division

Frequency division (FD) bat detectors synthesise a sound which is a fraction of the bat call frequencies, typically 1/10. This is done by converting the call into a square wave, otherwise called a zero crossing signal. This square wave is then divided using an electronic counter by 10 to provide another square wave.

[Or of course you could use an oscilloscope].

<<<[Or of course you could use an oscilloscope].>>>

Measure the time between any two peaks (one cycle) and invert the time to get the frequency. You can get better accuracy by measuring the zero crossing points and magnify the display.

26.3 microseconds (invert) 38,022Hz. The accuracy depends on the scope, but most of them are more than up to this kind of accuracy.

Many Radio Shack voltmeters have a frequency counter. This one will measure frequencies up to 4 MHz.