The basics for recording audio--


The microphone is the transducer used to convert acoustic sound into an electric signal that can be recorded and then later played back. Compared to most electrical signals the microphone signal is weak and must be amplified to be recorded.  Nearly all the devices used to record the electric sound signal are designed to accept a signal of a very specific signal strength.  The first skill in recording sound is to match the signal of the microphone to the requirements of the recorder.  This process is called ‘setting the level.’  The recorder sometimes has a signal level indicator that is used to determine if the incoming signal is at the correct strength.  The meter is most often marked with an optimal loudest level and may also have marks that indicate acceptable range, low level signal, and overly strong signal.   The general rule of thumb for setting levels is that the loudest part of the performance (the person or thing making the sound that is being recorded) should drive the indicator to the mark indicating the optimal loudest signal.

The exceptions and other considerations to the preceding are as follows:

  • Microphones of different makes and transducer types may have different signal levels.  They do all qualify as microphone level but some require substantially more or less amplification to be raised to the level required for recording.

  • Some recorders have the amplifier used to raise the microphone signal to recording strength built into the recorder itself.  

  • Some recorders do not have a signal strength indicator.

  • A specialized amplifier that is used to amplify a microphone signal to recording level is generally call a ‘pre-amplifier’ and will sometimes have an output level indicator and other signal controls to modify the signal before it is sent to the recorder.

  • The most useful signal strength indicators have a scale that are marked in decibels. A decibel is a measure of relative strength.  0 decibels means that the signal is unchanged (not amplified or attenuated) This 0db indication is the ideal peak level of a performance.   If you peak signal strength registers as -6db then your signal should be amplified +6db to be at optimal signal level to be recorded. If your peak signal level is registering as +3db then your signal should be attenuated (turned down) to be at the optimal signal strength level to be recorded.

  • Not only are these the optimal levels desirable for a signal to be recorded they are also the optimal levels for mixing.  So if a signal is inadvertently recorded at a level below optimal then it should be amplified so that it is optimal.  HOWEVER, if a signal is recorded at a strength greater than optimal then the signal will be distorted and can not be repaired.  The before mentioned distortion is of the form that the signal that is louder than 0db will be truncated or even inverted in strength and results in a harsh rasping noising sound that reduces the quality of the signal greatly.

As previously mentioned microphones are essentially a transducer that converts acoustic energy into electric energy. The transducers come in several different forms including: Dynamic, Condenser, Ribbon, Laser, Piezo, and others, but the two transducer types that are most commonly used are Dynamic and Condenser.  The most notable differences between these two microphone transducer types are that the Dynamic transducer generates its signal from the acoustic energy directly and the Condenser transducer requires additional electric power to create a signal.  This additional power can be in the form of a battery that is housed in the microphone itself, or it may be in the form of an external power source.  This external source is most often what is called Phantom Power (sometimes represented by a +48 indication) and may be supplied by a microphone preamplifier, a recorder directly, or even a sound mixing device.