There are many types of microphones available for different purposes. For accurate sound measurements
condenser microphones in combination with a unit converter (preamplifier) is widely used. Together they
have a superb frequency response and low inherent noise. This microphone set converts the sound
pressure to an electrical voltage that our analyser can handle.
- Free-field or Random incidence response
- Membrane size (frequency repsonse)
- Dynamic range (self noise and max SPL
- Temperature and humidity drift
- Polarization voltage
- Compatible preamplifier
When a microphone is inserted into a sound field it will influence this field simply because it
occupies some space. The microphone will reflect some of the incoming sound pressure and there
will therefore be a pressure increase just in front of the microphone. Some microphones are made
to give a response proportional to the pressure it senses (pressure field microphones) while
other microphones are designed to indicate the strength of the sound field as if it was not
present (free field microphones).
Whether a pressure- or a diffuse- or a free-field microphone is selected is often a function of
measurement task, tradition or a description in a measurement standard. Nor145 is usually delivered
with a free field microphone type Nor1225 in combination with preamplifier type Nor1209.
The Nor145 supports corrections when using a free-field microphone in a diffuse-field. This is called
Random-incident corrections and is available in the Input Channel menu. When activating this function,
a correction curve is digitally applied to the input channel.