Microphone behaviour depends on the acoustical environment, and on the way they are positioned and handled.
Microphones are typically developed and measured in laboratory environments like anechoic or reverberation chambers. The developer then can design his device to pre-determined demands. These are often a linear frequency response, measured with plane or spherical waves in the free and/or diffuse field, and constant directivity.
In use, in the studio and on stage we rarely find such idealized acoustic environments. The transducer is mounted inside a housing, held by clamps and stands, placed near reflective surfaces (e.g. music stands, human heads and bodies), and is often hand-held, while the singer moves around. All these factors influence the microphone’s response and behaviour.
The vocal performance itself is altered by the position of the hand on the microphone body. Other sound source signals (e.g. stage monitors, PA, other instruments on stage and in the studio) spill into the microphone. The effect on the spill, of hand, head and body can be even greater, and this affects not only the (diffuse sound) timbre but also the directivity of the microphone. As a consequence, also the achievable gain-before-feedback is typically reduced in stage applications.
It is thus essential to measure microphones in a variety of setups, representative of the acoustical environments they will be used in. These may include a set of near, mid and far field measurements, with and without acoustically obstructive items, like simulated heads and body parts, and in non-anechoic conditions. With such a set of measurements the transducer’s suitability for the intended application can be tested and confirmed.
Measured and recorded examples of the different acoustical effects will be presented and demonstrated.