Finding the Exact Frequency of a Piece of Audio

[fader8]

I've had several requests about how to find the exact frequency of various bits of audio, namely things like the initial tuning of a drum, which can be very elusive for a spectrum analyzer or impossible for a tuner plug-in.

 

Here's how to do it and it's very simple!

 

In the Sample Editor's View menu, choose Min:Sec:Ms:

 

Zoom in on your sample enough to clearly see the waveform. Swipe to make a selection between consecutive zero crossings, as shown:

 

In the top right of the Sample Editor, the length of your selection is shown in milliseconds. In this case it's 6 msec, (.006 seconds).

 

We would only ever select the full wavelength if we knew the signal was a constant pitch. If that were the case, we probably wouldn't need to do this exercise!

 

Since this selection is only one half of the wavelength, we need to double this time value to .012 seconds to determine the value in cycles per second (Hertz). Now open OSX's Calculator app and change the View preference to "Scientific".

 

Enter the wavelength duration and then click the "Inverse" key:

 

Presto! The frequency in Hertz of this kick's loudest fundamental is 83.3!

 

That wasn't so hard, was it?

Cheers, fader8

[Eric Cardenas]

Thanks!

Simple and easy as always señor ocho.

[ruari]

Bam!

 

As easy as that, thanks for that Fader8

[Jordi Torres]

I'm the operator with my pocket calculator!

 

 

J.

[fader8]

I'm the operator with my pocket calculator!

Gotta love those guys!

[BWTFFAM]

Very nice tip. Thanks.

 

Just one question: How come you don't select the whole wavelength from the get go? Why double? and I'm asking to know if there's a difference?

[David Nahmani]

How come you don't select the whole wavelength from the get go?

Because he wants to know the frequency of that very specific section, which is not the same as the frequency of the bit before.

 

Why double?

Because he's selecting only half a period.

 

and I'm asking to know if there's a difference?

Yes, there would be a difference since the length of the different half periods are not the same. Different wavelengths = different frequencies.

 

Just one question:

That was three questions.

[BWTFFAM]

hahaha touche

Since I've exceeded one already, Is there a way to find out the frequency range of an instrument throughout the song?

[fader8]

Is there a way to find out the frequency range of an instrument throughout the song?

Use a spectrum analyzer on that track. If the analyzer has a "Slow" setting, use it. These things have better frequency resolution when they have more time to make their measurements.

[BWTFFAM]

Thanks a lot! Does Logic Have a spectral analyzer? I had a look under Metering and then everywhere else but didn't find one. I found a Spectral Gate but that's obviously a gate.

If Logic doesn't have it, anywhere I can download one? (Freeware preferably, as I can't shop online)

 

Sorry for all the questions. I appreciate your time.

[ddi]

so can i just ask, does this mean the fundamental note is an E ??

[Eric Cardenas]

so can i just ask, does this mean the fundamental note is an E ??

 

Close to! I think an E is about 82.41 Hz.

[ddi]

i get it now.. just to be clear though, do we sort of ''round it down'' to the nearest note if the frequency isn't exactly spot on ??

 

sorry to be a pain .. this is very helpful to me though so thank you

[BWTFFAM]

Also, how do you determine the note when you know the frequency? Is there a simple formula to memorize?

[fader8]

just to be clear though, do we sort of ''round it down'' to the nearest note if the frequency isn't exactly spot on ??

Depends on what you're doing, and the workflow. Generally speaking, you should just do what sounds good.

 

Also, how do you determine the note when you know the frequency? Is there a simple formula to memorize?

Nice little java calculator here for that:

http://www.phys.unsw.edu.au/music/note/

Gives you the note with plus or minus cents, which is useful for tuning the sample, or tuning a synth to the sample.

 

Or you can plug it into the calculator. The formula for equal tempered scales is here:

http://www.phy.mtu.edu/~suits/NoteFreqCalcs.html

[route-electrique]

Thanks again Master. Will try this out and see how much are the analyzer plugins pissing on my eye.

[juniorspecial]

Here's a simple chart which shows pitch vs. musical note:

 

http://www.sengpielaudio.com/calculator-notenames.htm

[mrtapir]

Dragging this thread up again, with regards to Fader8's original method of swiping across half the wavelength, you pick the fundamental frequency right? And is this the wave portion with the highest amplitude?

[bengomisthebomb]

In Logic Pro X, I don't get to see how long the selection is (in your example 0:00:06), the new version doesn't tell you long it is...

[Eric Cardenas]

Make sure to use the Audio File Editor and not the Audio Track Editor.

[bengomisthebomb]

Yep, still no timer...

[Eric Cardenas]

I replied on your other thread. Please keep the discussion there instead.

[bengomisthebomb]

We would only ever select the full wavelength if we knew the signal was a constant pitch. If that were the case, we probably wouldn't need to do this exercise!

 

Since this selection is only one half of the wavelength, we need to double this time value to .012 seconds to determine the value in cycles per second (Hertz). Now open OSX's Calculator app and change the View preference to "Scientific"

 

I don't get this at all... How is it half a wave length? When clearly it's only about 1/12th of the full wave length?

[Eric Cardenas]

Here's the definition of wave length:

 

 

Where to do you get 1/12th from?

[bengomisthebomb]

Here's the definition of wave length:

 

 

Where to do you get 1/12th from?

 

Gee, thanks for all your help! He mentions that he had to double his 0.06 wave length because it's only 'half a wave length' + each wave in my kick is of different length, so therefore is my kick in lots of different keys?

 

Thanks for helping this n00b learn!

[Eric Cardenas]

What you are looking for is the fundamental of the drum.

A signal can contain many overtones.

By looking at the valley of the wave with the largest amplitude you are using the loudest part for your calculations.

This isn't always the fundamental but it is a good place to start.

[angelonyc]

Speakers work by moving rapidly out/in to make a wave form.. So they start at a mid point (as 0 volts ) and then move out (as a + voltage, and in (as a - voltage), to make the the first cycle.. It is this pushing and pulling of cone which makes the sound. Once the cycle starts moving above 16 - 20 cycles a second we begin to discern a pitch.. Middle A is the waveform crossing 0 volts 440 times a second. Faster and slower waveform crossings either above 0 volts, or below 0 volts will color the pitch (harmonics), otherwise a perfectly symmetrical wave form (out/in) would be a sine. I believe you need to look at the plus and minus voltage of the wave form to determine it's pitch properly. If you look at the first wave form you'll notice the above 0 volts is shorter in duration, then the minus voltage.. So doubling the below 0 voltage, is not going to give you an accurate viewpoint (rather earing point) of waveform cycle..

[nayam]

It is really easy and simple to do. Thanks for sharing.

[favdave]

The internet is full of hatred and ignorance...and then I find a thread like this where someone spends their time helping other musicians to make music and it gives me hope!

 

Thanks so much for this. Now all the other kids on my block won't make fun of my for having kick drums that are out of tune!!!