How to get a "CB" sound on a microphone

Question

I'm recording a track and the singer wants to get a real dirty sound on the vocals, like a static-y CB radio almost. I've seen some live acts get a decent sound by talking / singing through a toy battery-powered megaphone into the mic, but I'm wondering if there's an effect or processor or something I can apply to the channel to get that sound.

An example is this guy in the beginning and at 1:55

Another example (looks like using a pedal?) at about 28 seconds into this

Answer 1

An easy and inexpensive method that is commonly used is an Impulse Response processor, such as Ableton, TC Electronics Impulse Pedal, Voxengo VST plugin or the SciPy Signal Processing API.

The IR is especially good at modeling rooms and speakers, even small tinny speakers; such as found on a toy or CB Radio. It is sometimes called lo-fi audio: KVR Audio Forums,

Tall Guy Films - Make Your Audio Old-Timey/LoFi - AudioThing Speakers:

Video - TC Impulse Response Loader effects pedal

You can upload some audio to "VoiceChanger.io Online" and choose "Megaphone" (lower right) to produce a similar sound to what you are asking for without having to purchase or install anything.

Answer 2

Ok, let's go back in time when CB amateur radio was introduced. This was your signal chain:

• speak inside a (small) room, like inside a car // comb-filter
• transmit with quite limited bandwidth
• use high compression many times
• receive with limited bandwidth
• listen to a tiny speaker // comb-filter

Comb-filter effects arise from sound waves traveling different routes to the same spot, resulting in a difference in wavelength, resulting in amplification or anihilation. Just have a look at the drawings or listen to the audios. This is one major effect for this nasal and often hollow sound just look at the comb filters characteristics).

Bandwidth: try a low-pass with about 1.2 - 2.5 kHz, roughly; or replace it by a bandpass, to cut away some of the low frequencies, too, to emphasize the higher ones when listening.

Compression: It's basically a non-linear transfer characteristic, so you'll add a lot of distortion, hence overtones. Make sure, to suppress higher components enough by the filter.

So a simple setup looks like this:

• comb-filter (first set of parameters)
• compression (second set of parameters)
• bandpass (say ~200 Hz - 1.5 kHz, roughly) (third set of parameters)

This should give you enough complexity to vary sound and approximate what your videos show.

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P.S.: Short verification, using Ardour and Calf plugins with Linux

• right upper: signal chain Fader, comb filter, compressor, lowpass
• most important: comb filter
• lowpass to single out the singer
• almost irrelevant : compressor (bypassed)

Lower left shows you some impression of a comb filter. Set the two parameters, so it sounds a bit artificial, as wanted. Varying these two parameters while playing result in a phaser- or flanger-like sound.

Tuning the lowpass (lower right) close to the transmission limit of CB-radio, while introducing some resonance. This way focus on the singer is even more increased.

So with these 6 parameters (2 from comb filter, 4 from filter) a wide range of sound manipulation is possible, which your DAW can further automate, if needed.