Trying to remove a tone (called Code 33 tone) from police dispatch audio

I have a paid version of a website (and smartphone app) where I upload interesting police/fire audio into audacity so I can trim it, line up the tracks end to end and then truncate the audio.

When Law Enforcement works a priority event often the dispatcher initates a Code 33 tones. I have attached a .mp3 of the Code 33 tone

There is a 15 to 18 second gap between each Code 33 tone.

What I want to accomplish is this:

I want to completely delete the Code 33 tone from my tracks which are often hours long. I want to be able to select all tracks and with the click of the mouse delete all Code 33 tones. I have tried noise reduction under the effect tab to no avail. Everything I have down reduces the volumn of the Code 33 tone but does not delete it. I also dont want the deletion of the Code 33 tone to effect the quality of the audio.

I use .mp3 format not .wav

Im not sure why, thats just the way I have been doing it for years. I have read that .wav offers better quality but since what I do is just audio I dont know if it would make any difference.

I have also attached a screen shot of the Code 33 tones highlighted.

Thank you in advance for any help that can be provided.
Screen Shot 2019-03-06 at 2.18.06 PM.jpg

You can eliminate the tone with a 700 Hz Notch filter (, but that won’t deal with the “shhhh” noise or the massive click at the end.

The “shhh” noise could be reduced using the Noise Reduction effect (, but that is likely to do some damage to the audio that you want to keep because it is fairly high level broadband noise.

For the loud click, you could try the “Pop Mute” effect (, but that will only work if the click is substantially higher amplitude than the sounds that you wish to retain.

I use .mp3 format not .wav

If you get the performance and products you like, then you win. But you should know what the limits are.

MP3 is an end-product format. You can make an MP3 of an original performance (the radio) and unless you do something really evil, you will not be able to tell the difference.

If you open an MP3, edit it and then make another MP3, then the storm clouds gather. You are then double processing the sound and the errors could become audible: (bad cellphone, honky, bubbly, wine-glass audio). If you or someone else opens that sound and makes a third MP3, the sound quality will almost certainly be degraded, possibly useless, and the damage is permanent.

You can minimize the damage by selecting a very high MP3 quality setting such as 256 Constant or 320 Constant and use mono sound instead of stereo. That’s how the audiobook people do it. They make you submit sound with stupid-high quality MP3 settings in order to survive all the things they’re going to do to it later.

Or you could do everything in WAV up until the final posting which can be MP3. WAV format doesn’t have that progressive degradation.


What Steve said, plus equalization to remove everything above 4kHz & below 200Hz …

Reducing mains hum is optional.

steve, kozikowski and Trebor

Sorry for the late response, but thank you for taking the time to read my post and answering my question.