How to Make an Old Radio Voice Changer Filter in Audacity
Recreate the sonics of old timey radio equipment using only free and open-source software
In this guide, we’ll tell you how to create the sound of a vintage radio voice effect using the free audio software Audacity. You’ll need to use audio you’ve already recorded or have sourced elsewhere, as our guide will only show you how to process an existing sound to create a radio voice changer.
The sound of a radio can add depth and context to a piece of video, helping to convey a narrative and push a story forward, or merely adding to the ambience of a scene. Before we show you how to create your own, let’s talk about the reasons behind the typical radio’s particular sonic fingerprint.
As soon as we worked out how to broadcast sound, just having a radio gave you all sorts of benefits. The ability to listen to news or get new information – or merely just to keep yourself entertained while doing other things – improved people’s lives and their sense of connection to the world. A radio was a must-have piece of technology, so there were incentives to manufacturing them as cheaply and affordably as possible.
So older, more basic radios didn’t sound great to start with. Add to that the signal loss that happened when sound was transmitted over distance analog broadcast systems, and you have a recipe for bad sound quality.
A cheaper radio tends to use a smaller speaker than a professional audio setup. This means there’s a lot less bass in the sound the radio emits, which we can simulate using an EQ processor.
There’s also distortion involved in the sound circuits themselves. This is especially true in the radio is an old one. Electronics degrade over time and will lead to a crustier, more unreliable sound. This is easily recreated with a distortion processor, and we’ll show you how to do that using the one built into Audacity.
One final point to remember is that the original signal on a radio – sent by the broadcast station over the airwaves – will have been very different to a raw recording you’ve just made from scratch. Simulating the sound of an old timey radio will mean simulating a high-quality signal that’s coming through on low-quality equipment.
In the walkthrough below, we’ll take you through several steps that will help you create an old radio voice changer in Audacity.
Beginning with some EQ, we will simulate two of the most common properties of old radio technology like this. The lack of low frequency sound output and the extra resonances associated with lower-quality or aged equipment.
Next, we apply some compression to the sound in order to simulate a real radio broadcast signal more realistically. This is necessary on a raw voice recording but may not be necessary if you want to make a piece of music sound like it’s coming out of the radio. Music will be broadcast just like it sounds on the original recording, whereas the signal from a radio presenter’s microphone will be subject to some treatment before the signal is sent. This part of the tutorial will emulate that treatment for voice.
Finally, we will add some grungy distortion to our sound – in a tribute to the fact that an old radio’s circuitry will be worn out and of lower quality.
We’re starting with a voice recording, but any audio material will work for this – anything that could realistically come out of a radio!
Start by making sure the audio is up-to-scratch to begin with. We’ve used the ERA Bundle 5 on the raw recording in order to remove background noise and reverb, and to do some minor de-essing work.
Next we use Audacity’s Effect >> Normalize function to increase the volume of the audio so that the highest portion is as loud as it can be without going off-the-scale. Actually, we set the highest point of the audio to -1.0dB, as is Audacity’s default option.
Now it’s time to mess with the frequencies of the audio, so we grab a Graphic EQ out of Audacity’s Effect menu.
An old radio will have a different frequency response to a high quality modern speaker. Depending on the size of the speaker, it won’t have much bass response, could sound quite tinny, and also might have a lot of resonance in one area. You don’t need to know this technical jargon to get it right – just stick with us for this tutorial!
We’ll start by removing low frequencies. This simulates the smaller size of speaker in a consumer radio. It’s possible for radios to reach these frequencies if they’re built with a large-enough speaker, but if you want that vintage radio voice effect, you’ll want to make it tinny!
By reducing all the dials on the left to their minimum (above), we remove the lowest, bass frequencies from the sound. We’ve removed everything from 315 and below to really emulate that radio sound effect. Check out the Preview function on your current setup to see how it sounds as this is being done.
We’ve also created a slope up with bands 400 and 500, and overshot the right-hand flat line by raising bands 630, 800 and 1k in the shape shown below. If you want to know the technical details, this adds a resonant peak that corresponds to the size of the consumer speaker we’re emulating.
For that extra bit of dirt, we also raise the highest frequencies over on the right-hand side a little. This helps to make the sound even more crisp, and it shouldn’t interact with any dialogue happening anywhere else in your soundstage.
We do this to emphasize how a small radio speaker will be dominant in this high frequency band at the top of the audio spectrum.
Now we open the Compressor from the Effect menu in Audacity. This is most reliable for voice recordings. Remember, an actual radio station signal will be broadcast with a higher-level, more powerful signal than your raw voice recording. The audio will have already been compressed by the broadcast-quality gear, and luckily we can recreate this effect right in the Compressor.
Set a Ratio of 2.4. The default Attack and Release times (as shown in the image below) should work fine. The sticky wicket here is the Threshold control. This will have a different effect depending on the current volume of your audio (it helps that we Normalized this recording at the start of the process). Lower the Threshold and try to hear how much ‘stronger’ it makes the audio signal, even if it’s not coming through at a different level. We’ve set ours at -32dB.
After compression, you can see some differences in the audio waveform. The highest peaks are still quite similar to the height they were before, but the lowest portions have been brought up to a higher level, making them look chunkier.
Now it’s time for the coupe de grace in the creation of an old radio voice changer – some distortion! This stage adds some grit to the signal, indicating the lower-quality circuitry that you would find in a dodgy old radio.
Go to the Effect >> Distortion option in Audacity, and select the Hard Overdrive option from the Distortion Type menu. Play with the Preview function a little to test out the effect of this Distortion processor, but we’ve managed to crank ours all the way up to the maximum of 100.
Using our Mauvio app for iPad and iPhone, you can recreate a set of sounds in seconds, including an old radio sound effect. Just load your audio, and a few taps are all it takes to enhance, de-noise and add special effects to any sound.