Whether you realise it or not, if you are producing any kind of audio output, on air, online or on demand, then you are playing with loudness. You have probably noticed that when you flick between stations, podcasts, YouTube videos or any other content that has audio, the volume coming out of your speakers is jumping around. This is due to different loudnesses. But what is it, why is it important, and how do you fix it for you student radio station?
What is loudness?
If you search for a definition of loudness, most of them are full of jargon. In short, it’s how loud or quiet audio is perceived to be. This is different to the volume or level of the audio, because it’s measured across frequencies and is related to how humans hear sound. If you think back to GCSE Science lessons, you might be able to recall that humans have a hearing range of around 20Hz to 20kHz (reducing as you get older). However, that ability is not equal across all frequencies – we are most sensitive to 2000-5000Hz. That isn’t all – other factors such as length, timbre and volume of a sound can all affect its loudness.
In case this still doesn’t make much sense, here’s a practical example. In this clip, the same note plays with short intervals at -1.5dB, and then again at +1.5db with longer intervals. However, you should hear it as roughly the same level throughout, because the shorter gaps mean we perceive it to be louder.
Why is this important?
Each studio and each station has a slightly different set up: different mixers and mics; different processing; different transmission path. This means that for the listener at the other end, as they flick between channels, there will be a change in loudness, with the potential of them having to turn their speakers up and down as they go.
If a station is too quiet, the listener may have to turn up their speakers enough that they become noisy, or they might choose to just skip over the station altogether. Meanwhile, a loud station jumps out at the listener and grabs their interest. A louder station often sounds bassier than a quiet one, and appeals more to human ears.
The amount of effort required to listen to something also affects whether a listener will stick with a station – if they have to keep changing the volume as it gets louder/quieter, or can’t hear certain things over the environment they are listening in, they are more likely to listen to something else. This is affected by both the levelling of different audio sources and the overall processing after.
How can you fix this for your student station? (This is where this gets a bit more technical!)
Firstly, you need to work to have consistent and suitable loudness. By ensuring content (recorded and live) is well produced (good levelling; a sensible and fairly consistent loudness), and combining this with processing the output prior to broadcast, you can achieve great results.
Achieving good levelling comes with practice and listening to your output. That being said, it is possible to put some numbers down on a rough guide to get you started. This table uses a PPM meter for peaks (normally found on a broadcast desk, most audio editing programs will have a way of showing this). It also uses dBFS for the average normalisation level, which is the default reading for most audio editing programs, and is also often seen on broadcast mixers. This covers both pre-produced audio and live studio mixes.
Even with good levelling, your output might still sound quieter than other stations. This is where processing comes in. Processing can be applied in various places to ensure good audio throughout the chain from audio source to transmission.
The key here is compression. A compressor can be used to reduce the level of the peaks and increase the level of the low bits, bringing everything to a more consistent place. Compression can be a bit of a dark art, so experiment and see what works for your station and systems.
A word of warning though… compression should not be the only step here. It can only come after good levelling, as heavy-handed processing can cause listener fatique, which isn’t great!
The European Broadcasting Union (EBU) recommends a target loudness of -23 LUFS (the unit of loudness). Other sources recommend around -18. However, this can be quite hard to measure against on audio equipment – it will normally show you it’s output in some form of dB reading. A good way to measure your broadcast is to have the same audio that’s going out to your transmitter routed to the input of a computer (this can just be to generate the online stream, or a separate input). You can then use a tool to measure what’s actually going out.
I recently came across the ‘Orban Meter’. It uses LKFS as the reference reading (effectively the same as LUFS), as well us having a VU and PPM meter. You can find it here: https://www.orban.com/meter There are other tools around, and most audio editing packages contain metering tools as well, but this one seems to be quite reliable once you’ve selected the correct sound source in the settings.
Once you’ve set yourself up with a sensible loudness (you can also use the tool to see what an online stream is doing, so you could compare yourself to a national station) make sure you listen to your broadcast again… just looking at the meters doesn’t guarantee a good sound. You might also need to adjust the output from any processing up or down a bit after you’ve got the loudness/processing correct.
Loudness and processing are quite complex ideas to get your head around. I’ve tried to keep this basic and easy to understand/use but there’s still a certain level of depth that needs covering. Any questions, I’m happy to go into more detail or explain more in email: firstname.lastname@example.org