Radio Amateurs Old Timers Club Australia Inc
Registered No A0042780C

VK3OTN Broadcast 

  Production

• Audio should be recorded as a 16 bit 44.1 kHz mono, linear PCM file, using no software compression whatsoever when saving the file. This is effectively the same quality as used by audio compact discs. CD's, however, are actually 14 bit stereo, linear PCM.
• Ensure the audio being recorded is less than the peak input level of the peak reading meter, otherwise distortion will be introduced. Softer sounds can easily be fixed up with software.
• Audio should then be normalised, that is the peak of the signal is plus and minus unity, or full scale.
• It is possible to use software to lift the perceived loudness of the recorded audio. Usually 3 or 6 dB is all that's needed, The peaks will be clipped, however the signal will suffer minimal distortion and the perceived loudness should be improved. It should sound natural.
• An external VU meter, or better still a software VU meter can give a good visual indication as to the loudness. Just because the audio is normalised on the various segments that combine to produce  the broadcast, it doesn't mean it will all sound the same. One well known example is LOUD TV commercials. The audio is at the same peak level as the program being broadcast, however a few simple tricks are used to make it sound louder in order to make you sit up and pay attention. The audio of the entire broadcast should have the same level, or perception of loudness, as heard by the human ear.
• Ensure the room the audio is being recorded is acoustically quiet. No dogs, magpies, budgerigars - or other noisy pets for that matter – or rain on the tin roof; also don't forget to silence or move any ticking clocks
• Use a quality microphone. A combined microphone and headphone 'headset' is one option. This way the microphone is a constant distance from the mouth. Desktop condenser microphones start at around $25 or so. A USB microphone, which plugs directly into the PC is one option. The A to D conversion takes place right at the microphone so it is not possible for electrical noise to be introduced. A windsock on whatever microphone is used is also a good idea to reduce breathing sounds and other artefacts.
• Prepare what you are going to read on a word processor by typing it out precisely how you intend to say it. You can either print it out, or read it directly off the screen. Ensure the font size is nice and big, thus making it easy to read.
• Very experienced readers (an example is professional news readers we hear and see on broadcast radio and television) can read a script faultlessly. This only comes about from years of practice. Unfortunately, most of us don't have that experience and will stumble and make mistakes. Umms, errs and stuttering are common errors. Don't strive for perfection and don't stop recording. Simply leave a short pause and start again at the beginning of the sentence. The mistakes can be easily removed with software later on. If you're reading an article or story, do the recording in one continuous session. Don't attempt to do one article using several different recording sessions, hoping to join the two or more recordings together. When you join the various segments together, a difference will be noted.
• If sending a segment to whoever's producing the finished broadcast file via email, and if the file is greater than four minutes in length, around 20 MB, then use mp3 compression. Use a 256 Kbps bit rate, and leave the sample rate alone at 44.1 kHZdio