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For those of us in broadcasting longer than we care to mention the phrase “watch those levels” rates up there with “keep off the grass”. We know we should obey but aren’t quite sure why or sometimes how ! If your name is George Hook or Tom Dunne then you’re free to go now we won’t delay you any further because you have producers and sound engineers to look after these trivials for you. Everyone else please stay seated, thank you. In fact those superstars of radio would laugh at the thought of it but for us mere mortals of budget broadcasting it’s an important part of out daily work.

I’ve no intention in making this an uber technical artical but I would hope by the end of it you will have an appreciation for those little VU Meters on the mixing console in front of you. You hopefully will realise they’re not simply waving to you but imparting some important information that directly effects how you sound on air and importantly whether the listener – your listener – sticks around to enjoy your station.

VU Meters on a mixing console serve two main purposes. Firstly they are an indication that you are actually broadcasting something – that you’ve not forgotten to punch up the slider or hit PLAY on the CD Player – we’ve all done it. The dreaded Dead Air syndrome ! This is very importand if the monitor in your studio doesn’t let you hear the mixer output but only what your cans output.


Typical Airmate mixing console used in local radio stations.

Secondly, they display the releative level of the program being broadcast. This is the important bit ! Think of yourself as a listener to radio for a moment. If your listening to, say, Newstalk you are being attentive to every word being said. You turn the volume up to a set level on the radio and listen, if you’re moving away from the radio you might increase the volume so you can still here the program from your new location. Music radio is different. Music tends to be in the background and a set level comfortable for humming along to. A familiar tune will trigger memories in the listeners mind and they may hum or - heaven forbid in my case – sing along ! Hands up who hasn’t roared along to a tune playing in your cans oblivious to those around us . . . that’s what I thought.

 For the most part this is what we aim for as hospital stations – to entertain in a relaxing way. What we don’t want is to make our listeners work too hard or be uncomfortable. On those occassions where we broadcast an interview or other general interest shows not comprising of music then our Mic technique is tested – more on this in a later tutorial.

Back to our listeners and those VU Meters. In most cases radio programmers will have a set source for music material, CDs, vynil, mp3 or .wav files are all common formats. Some stations will only permit one format, usually station supplied and sourced cds. Many stations – St. Ita’s included – make extensive use of mp3 format stored on a central server accessed by the presenter. (see glossary below)

Those using vynil will have a different set of problems to deal with, the levels between 33.3 RPM albums, 7” singles and 12” singles vary hugely so listen up !

Commercial cds are recorded and processed in well equipped studios and mastering plants to have a reasonably constant sound level across the particular disc. A cd made from our own compilation of tracks from several different discs or downloaded mp3 or wavs won’t have this uniformaty without some intervention from you. We intend to do a tutorial on audio editing at some stage in the future, these techniques will be covered in more detail then.

MP3 files obtained from the internet range from barely audible up to damn loud or some where in between, they may also suffer from over conversion (see glossary below).

These are the reasons we need to pay close attention to those VU meters. The last thing we want is a patient having to constantly reach over to turn up or down the volume in order to hear the program – your program. Pretty soon they’ll get uncomfortable and simply change the channel. Coming out of an intro into a song with a low VU level into a song whose volume is considerably higher isn’t a pleasent experience for your listener.

All stations in the IHRN, indeed all stations under the BCI, are required to obey the rules about Frequency Deviation (see glossary below). This is a measure of how efficiently we use or abuse our permitted frequency range on the band. VHF FM stations are permitted a +/- 75KHz deviation. Many of you are probably scratching your head right now but suffice to say the closer we adhere to this figure (without exceeding it) the more consistant the sound of our station and the less chance of us being reprimanded by the BCI.

Commercial stations employ expensive sound processors on remote sites and use digital techniques to constantly monitor and adjust sound quality/level. Us lesser mortals for the most part don’t have those luxuries and may simply employ a compressor/limiter (see glossary below) to prevent over modulation and to hopefully make up for some deficiencies in the program material.

No matter how good these devices are there is still a responsibilty on our part to ensure that what we are doing isn’t adversly effecting the stations sound or causing us to breach the BCI rules or worse still make our listeners uncomfortable and ultimately tune away.

Most modern mixing desks use either an Analogue or LED type VU meter. Some employ a PPM or Peak Program Meter (see glossary below). Below are examples of both types.

vu meter

Analogue VU Meter


analogue ppm

Analogue PPM


A common feature of both VU types is the Red zone or ‘no go’ zone as we call it. Sound is very dynamic, that means it’s level and frequency can change constantly in music form. To reflect this the needles of the analogue meter or the brightness of the LED meter will move/vary in unison with the content of the signal. Generally it is desirable to avoid prolonged excursions of the needle or LED into the red area of the meter. If they are constantly being reached then you need to pull back the slider so that the indicator reaches the 0db area or in the case of the LED meter, the yellow indicator. Also if the program stays in the lower areas of the meter then we need to increase the level by pushing up the slider. The desired result is a reasonably constant level in or about the 0db level. Doing this gives the other processing equipment less to do, improves the overall quality of the audio and makes for a more relaxed listener who sticks around.

Of course this doesn’t only apply to music content. Your Mic technique will also effect the level when you speak. Sitting back from the Mic will result in a hollow weak sound lacking in punch or definition and professionalism, while getting too close sounds muffled and suffers from plosives (see glossary below). Also, trying to shout over the intro or outro of a track will send those needles flying and deafen your audience – use the slider to bring back the music to a lower level. Don’t fader bash !!! Listening to FM104 it might sound like the presenter is adjusting his slider in between sentences (fader bashing), he isn’t, that’s the processors automatically adjusting the audio to keep that deviation thing we mentioned earlier constant.

Again monitor the meters, aim for the 0db mark and avoid sitting too close or talking directly into the Mic. A plosive shield is also a good investment but there is no substitute for common sense and good technique.


plosive filter

Plosive filter fitted to a Capacitor Microphone.

Hopefully I’ve imparted some useful and hopefully accurate information here to help improve both you and your audiences experience of your station. I’ve provided a glossary of terms used so you can check them out in a little bit more detail if you wish. The moral here is monitor those meters and adjust the slider to correct any discretions in the signal. If you know your music then you’ll know songs that start low and get louder so you could leave the low parts as they are but prepare to adjust the higher sections. Remember no one like to talk to themselves, follow these simple tips and you’ll be assured that if your listeners have gone then it’s probably just becuae it’s dinner time – they’ll be back !

Feel free to comment or correct any aspect of this article or indeed add your own experiences or techniques that others might benefit from. Tom has informed me that this article may be peer edited by some of the more knowledgable engineers on the other stations – feel free guys. This will hopefully result in a good quality reference article for all to read.

Is mise

Cionnaith MacAodh


What is an MP3 file ?


What is a server ?

A server in this context is simply a computer with a large storage medium e.g. hard disk drive, connected to and accessible by other computers on a local area  network. This can be more desirable in the broadcast environment as it allows the station manager to review tracks for quality, appropriateness and expletives. It is also possible to protect files from accidental deletion by setting permissions on a per user basis thus protecting that valuable resource. The presenter will have access to the media via a computer on the desk and suitable software such as BPM Studio (see glossary below) or WinAMP. It can also provide the basis for an extremely effective overnight or holiday music system during periods such as Christmas, bank holidays etc.

Frequency Deviation:


Audio compressor/limiter. Dynamic Range Compression :


The PPM or Peak Program Meter.



Those P sounds that drive compressors and mixers mad and are the bane of audio engineers the world over !
More info here: http://blog.timcurran.com/?p=208

BPM Studio Homepage: