calibrate

Calibrate meter using calibration tone with known level

Syntax

calibrate(SPL,micRecording,SPLreading)

Description

calibrate(SPL,micRecording,SPLreading) sets the CalibrationFactor property of the splMeter object. The calibration factor is based on the computed sound pressure level (SPL) of micRecording and the known SPLreading.

To calibrate, first set the SampleRate property of the splMeter object to match the micRecording, and the PressureReference and FrequencyWeighting properties to match the values from the physical SPL meter.

Input Arguments

SPL — splMeter System object™

object

splMeter System object to be calibrated.

micRecording — Audio signal used to calibrate microphone

column vector

Audio signal used to calibrate microphone, specified as a column vector. micRecording must be acquired from the microphone you want to calibrate. The recording should consist of a 1 kHz test tone.

Data Types: single | double

SPLreading — Sound pressure level reported from physical meter (dB)

scalar

Sound pressure level (SPL) reported from physical meter in dB, specified as a scalar.

Data Types: single | double

Algorithms

To set the CalibrationFactor property on an splMeter object, the calibrate function uses:

• A calibration tone recorded from the microphone you want to calibrate

• The sample rate used by your sound card for AD conversion.

• The known loudness, usually determined using a physical SPL meter.

• The frequency weighting used by your physical SPL meter.

• The atmospheric pressure at the recording location.

The diagram indicates a typical physical setup and the locations of required information.

The CalibrationFactor property is set according to the equation:

$$\text{CalibrationFactor}=\frac{{10}^{\left(\left(\text{SPLreading}-k\right)/20\right)}}{\mathrm{rms}(\text{x})}$$

where x is the microphone recording passed through the weighting filter specified by the FrequencyWeighting property of the splMeter object. k is 1 pascal relative to the reference pressure calculated in dB:

$$k=20{\log }_{10}\left(\frac{1}{\text{PressureReference}}\right).$$

Version History

Introduced in R2018a