A sound engineer will be expected to operate & be familiar with many different pieces of electrical equipment. Luckily, many of us already have some experience with sound equipment, most notably our hi-fis, stereos or home entertainment systems. Here too audio signals are travelling down paths.

Consider an average stereo system. Typically this would consist of a CD player, a radio tuner, a minidisc recorder & even a place to connect an MP3 player. (See diagram below.) You, as the operator, have the ability to control the signal path. Each component would have its outputs connected via phono leads to the inputs on an amplifier. Typically, you would only wish to listen to one audio source at a time, therefore the sound system would have buttons to select which source you want to hear – CD, radio tuner, MD or MP3. The one you select will then have its audio signal sent to the speakers. You only ever hear one source at once & that is usually the way you would want it. Why would you possibly want to listen to a CD & an mp3 at the same time?

Here we can see the CD player is selected as the source indicated by the green light.


You will probably have some way of controlling the volume of the sound you have chosen to listen to & you may have the ability to change the quality of the sound in some way. Most sound systems have controls labelled “bass” & “treble” while some will also have a third control for “mid.”

Let us consider for a moment what these controls do. When you turn up the control labelled “bass” in essence what you are doing is turning up the lower frequencies of the music you are listening to. In pop music the instruments that produce the most bass (or low) frequencies are the electric bass guitar & the bass drum. Consequently when you turn up the “bass” control you will hear more of these "bass-y” instruments.

When you turn up the “treble” control you are turning up the higher frequencies in the music. In most pop music this will result in instruments such as acoustic guitars & cymbals being accentuated as they have lots of high frequencies. The “mid” control will, as you would expect, turn up the middle frequencies.

Have a listen to the example below. It is a four bar loop. When it repeats the second time you can hear the treble has been turned up resulting in a "brighter" sound with the acoustic guitar & cymbals more apparent. The third time we have turned the treble back down & the bass up. Now you can hear a "weightier" sound with the bass guitar & bass drum more apparent. The fourth time the loop repeats, the mid frequencies have been turned up. What instruments now stand out?

(Please use headphones to listen to the audio examples.)