Creating a radio effect using a convolution filter

Using the Impulse Response

In order to use this impulse response we need to load the “Room Simulator” effect into our target audio track (containing the speech we want to process) and then we load the impulse response into the effect instance. Here is the Room Simulator with the target impulse response loaded. Note that we configure 100% on all Impulse IR parameters and also Spectral Edit. We don’t want to modify the impulse response in any way at this stage. It should be noted that for Sequoia, these parameters are more suited to a “reverberation-type” impulse response and consequently allow trimming of early and late reflections present in the IR. We’re not interested in trimming these. What we do want to configure is the Dry/Wet ratio – we want 0% DRY and 100% WET for the output – we don’t want to mix in any of the original signal and are only interested in hearing the processed signal through the convolution filter.

RoomSimulator

Here’s some examples of the original sound and the resulting sound after processing.

Original Voice Recording:[audio:http://104.198.4.5/wp-content/uploads/2013/01/MK41-original-male1.mp3|titles=Original Voice Recording]

As received RAW through target signal chain:[audio:http://104.198.4.5/wp-content/uploads/2013/01/UnidenFM-Transmitted-male.mp3|titles=Voice through Target Signal Chain]

Original Voice Recording processed through convolution filter:[audio:http://104.198.4.5/wp-content/uploads/2013/01/MK41-convolution-male.mp3|titles=Voice through Filter]

Adding the Trimmings

Now we have our “processed” audio which sounds remarkably like it has just been received over the FM CB Band, we need to add in a few trimmings to make things a little more authentic.

Firstly, It’s also a good idea to EQ the incoming signal after sending it through the room simulator. It may also be necessary to add some compression, however the best solution here is to use your ears to compare the raw transmitted sound with the sound coming through the convolution filter. Here’s the EQ curve I used.

EQCurve

Original Voice Recording processed through convolution filter with EQ and Compression:[audio:http://104.198.4.5/wp-content/uploads/2013/01/MK41-convolution-eq-compression-male.mp3|titles=voice through filter]

Secondly, our signal doesn’t quite have the noise-floor that the original transmission does. Nor does it have the “Squelch” noise at the end of the transmission. This can be simply fixed up by recording some transmitted silence through the same signal path along with the “Squelch” noise and editing this into the DAW audio arrangement, setting the mix levels appropriately.

This is the waveform representing the “trimmings” that we will mix into the final output.

 

trimmings

This is what the “trimmings” sound like on their own:[audio:http://104.198.4.5/wp-content/uploads/2013/01/trimmings.mp3|titles=Trimmings]

Original Voice Recording processed through convolution filter with EQ, Compression and “trimmings”:[audio:http://104.198.4.5/wp-content/uploads/2013/01/MK41-convolution-eq-compression-trimmings-male.mp3|titles=everything]

Comparing this with the result that was simply got by recording the Uniden receiver as we were recording the test speech, I’d say we’re pretty close:

[audio:http://104.198.4.5/wp-content/uploads/2013/01/UnidenFM-Transmitted-male.mp3|titles=Radio Voice]

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