Public Address 'Tannoy' effect

This effect simulates a megaphone or ‘Tannoy’ system, such as used at outdoor events. Lots of tweakable parameters that should be fairly self-explanatory.
Here’s a before and after, using the default settings for the ‘after’:

The plug-in:
PublicAddress.ny (1.69 KB)
Installation instructions:

Please post feedback, reviews and bug reports as replies to this topic (click the “Post Reply” button).

Feedback? “Everybody knows” PA systems have to feed…eeeEEEEEEEE!

Just like “everybody knows” radar has to go 'round and 'round, etc.


That’s a separate effect, but easy to use and requires no additional download.

  1. Enable “Software Playthough”
  2. Start recording
  3. Take off headphone
  4. Put headphones over microphone
  5. Take headphones off microphone, and stop the recording.

Mix that into the start of the voice recording, then apply the “Public Address” effect.
How did you get on?

I’m nitpicking here, but shouldn’t each echo should have less high-frequency content than the previous one, e.g. …

You wouldn’t necessarily need to add another slider: the low-pass effect would be proportional to the echo delay time.

Yes, to sound more authentic, it should, but have you looked at the code?
It’s a pretty simple effect, with the heavy lifting (except for the final “normalize” step) handled efficiently in Nyquist’s DSP primitives (written in C). The advantages of this are speed, efficiency, and only a small amount of Nyquist code.

The downside is that there’s only a limited amount of customisation of the DSP units available. In particular, it’s not possible to insert additional processing within the delay loop. Nevertheless, when the echoes are kept reasonably low compared to the reverb, I think the effect is pretty good for such a simple and convenient effect.

It IS possible to construct feedback delay with a low-pass filter inserted in the delay loop, by writing the loop as a LISP loop, but I was really interested in doing this with the built-in primitives.

As always, thanks for your feedback Trebor (pun half-intended :wink:


I maybe being dim here…but i have downloaded your plug in which is exactly what i need) Enabled it in plug ins and attempted to use it on a track.

However, no matter what settings i choose, it doesn’t seem to alter the audio. Other plugins work fine.

Is your plugin dependent on something else that i’m missing?

Any guidance appreciated.


What sort of sound are you trying to use it on?
Which version of Audacity? (Look in “Help > About Audacity”)
What sort of speakers / headphones are you listening with?

When you run it, click the “Debug” button instead of the “OK” button. If it shows you an error message, copy and paste the error message into your reply.

If a short echo length (time) is selected, and reverb is off, the result is like a blues vocal mic …
Blues-mic settings.png

That’s cool Trebor.
The high frequency roll-off is the most obvious effect, but then the short delay adds “something else” which is hard to put your finger on just from listening.

It’s effectively a comb filter