Transfer factor
The electroacoustic transfer factor B E of a sound pick-up is the sensitivity ( English responsivity ) with which the sound pressure of microphones - that is sound receivers and sensors - is converted into electrical signal voltage ( modulation voltage ). The sensitivity is often referred to in data sheets as the field operating transmission factor or field no-load transmission factor and applies - unless otherwise specified - for the frequency 1 kHz .
The factor B E represents the relationship between the generated electrical alternating voltage U and the sound pressure p at 1 kHz, expressed in mV / Pa and is an essential quality mark of electroacoustic transducers :
The higher the transfer factor, the more the electrical output voltage U at the microphone increases while the sound pressure p at the input remains the same . The usual B E value of a condenser microphone is around 10 mV / Pa and is significantly lower for a dynamic microphone at around 0.5 mV / Pa.
Figures in the USA
In the USA the transfer factor is z. In some cases, do not specify mV / Pa in the SI unit , but rather as sensitivity in dB or in where the dB values are negative.
Usual information, depending on the selected reference value:
- Condenser microphone: about -40 dB or -60 dB
- dynamic microphone: about -66 dB or -86 dB
Reference values:
- the sound pressure p = 1 Pa corresponds to a sound pressure level of L p = 94 dBSPL (1 Pa → 94 dBSPL).
- the sound pressure p = 1 dyn / cm² corresponds to a sound pressure level of L p = 74 dBSPL (1 dyn / cm² → 74 dBSPL).
Transfer factor for amplifiers
In the case of an amplifier, the gain or the transfer factor is defined as the quotient of output and input voltage:
This definition does not require a reference measure, since the input and output variables have identical units.