Audio Engineering Session 4

In this blog I would like to welcome my fellow AE students! Hopefully these blogs will help you as much as they help me. I should point out however that this blog is primarily written to re-enforce my understanding of the AE sessions. Certain information may be missing as I may have already gained this knowledge. Therefore it is important to say that this blog should not be a substitute for your own notes but rather a supplement to them.

This weeks session began with a discussion on WAV files. We took a look at a variable waveform in ProTools. Zooming in on the wav file we were able to see the peaks and valleys. It was pointed out to us that the waveform includes both amplitude and frequency information. The image to the right displays a typical waveform as viewed in many audio software applications. The image to the left displays a zoomed in image of the waveform. The jagged edge displays the frequency while the overall shape of the wave represents the amplitude.

Next up in our session was to learn about microphones and how a microphone operates. The example we looked at was a Shure SM58 dynamic microphone which is a staple in most every studio. The SM58 is known for it's ruggedness and it's ability to perform well on stage.

Microphones are a type of transducer which is a device that converts energy from one form or another. Microphones convert acoustical energy (sound waves) into electrical energy (the audio signal).
Different types of microphone have different ways of converting energy but they all share one thing in common: The diaphragm. This is a thin piece of material (such as paper, plastic or aluminium) which vibrates when it is struck by sound waves. In a typical hand-held mic like the one below, the diaphragm is located in the head of the microphone. When a magnet is moved near a coil of wire, an electrical current is generated in the wire. Using this electromagnetic principle, the dynamic microphone uses a wire coil and magnet to create an audio signal. The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates a current in the coil which is channeled from the microphone along wires.

Loudspeakers perform the opposite function of microphones by converting electrical energy into sound waves. This is demonstrated perfectly in the dynamic microphone which is basically a loudspeaker in reverse. When you see a cross-section of a speaker you'll see the similarity with the diagram above. In fact, some intercom systems use the speaker as a microphone. You can also demonstrate this effect by plugging a microphone into the headphone output of your stereo, although we don't recommend it! I have an old speaker that I have wired up to be used as a kick drum microphone and it works quite well in that application.

Well folks, that is about it for now. I will update this post at a later time. Discussion on the DI Box, gain staging and a look at the Shure KSM32 will be added at a later time.

*REMINDER: There will not be a session next week.