# Extracting a frequency from an audio signal sent through a microphone?

#### Green Bean

Joined Mar 31, 2017
126
If I have a mic connected to an on-board mic input, how do I extract the frequency from the voltage? I'm assuming audio signals sent through cables like this

are analog. In that case. how does one extract a frequency from the voltage sent through the cable?

#### #12

Joined Nov 30, 2010
18,217
With a capacitor.

#### BR-549

Joined Sep 22, 2013
4,938
The "frequency" is the CHANGE in voltage. We don't want to separate it from the voltage. We want to multiply it......amplify it....increase it.

If we take the change of the voltage away........nothing will come out of the speaker.

An amplifier.........takes a small wiggle of voltage and makes a bigger wiggle of voltage.......so that it can drive a speaker.

The pattern or shape of the wiggle.......is what is made larger.

#### Dodgydave

Joined Jun 22, 2012
9,941
Three posts in as many days, must be a ....

Moderator's note: Derogatory term removed/. -dc

Last edited by a moderator:
#12

#### Green Bean

Joined Mar 31, 2017
126
So this all makes sense. What I need to do now is convert the analog signal to digital. Is there a IC used specifically for these audio cables and their outputs? And what's the voltage range of the output anyway? I'd like to make a circuit that takes the audio output of my phone (through an audio cable like the one pictured in post 1) and converts it to a digital signal that is shown by some LEDs.

#### shteii01

Joined Feb 19, 2010
4,644
So this all makes sense. What I need to do now is convert the analog signal to digital. Is there a IC used specifically for these audio cables and their outputs? And what's the voltage range of the output anyway? I'd like to make a circuit that takes the audio output of my phone (through an audio cable like the one pictured in post 1) and converts it to a digital signal that is shown by some LEDs.
To digitize analog signal you use Analog to Digital Converter (ADC). There are hundreds of ADC chips, some are made specifically for audio, but you don't really need anything audio specific, any ADC chip with 40 or more kHz sampling rate would be good enough.

You can google the range of the voltage that the phone puts out from audio jack.