You can use this analysis object to calculate the sharpness of a stationary or time-varying sound signal.

The Sharpness of a sound is an auditory sensation which describes the particular aspect of the tonal perception that is correlated with the frequency distribution of the spectral envelope of sounds. The sharpness is a psychoacoustic variable and is determined by calculating the loudness.

Type of input data

The Data tab is where you specify how the input data is to be interpreted. A microphone sensitivity of 50 mV/Pa is used for the conversion between voltage values (V) and sound pressure values (Pa). For more details, refer to Calibration in Acoustics.

Supported Types

•The input signal is the third-octave spectrum. The third-octave spectrum must be a data series or signal with 28 third-octave bands for frequencies between 25 Hz and 12500 Hz.

•The input signal is the measured voltage signal of a stationary sound.

•The input signal is the measured voltage signal of a time-varying sound.

•The input signal is the measured sound pressure signal of a stationary sound.

•The input signal is the measured sound pressure signal of a time-varying sound.

Calibration

To deduce the loudness from the microphone output voltages recorded, the microphone sensitivity and the gain of the whole signal chain must be taken into consideration. This is done for example by generating a specified sound pressure level at the microphone using a calibrator. This analysis object supports the following working methods:

•If you want to determine the calibration using a calibration measurement, choose Obtain calibration from data set and then specify this calibration measurement as a calibration data set as well as the level of the calibrator (Calibration level). The level must remain constant for at least 4 seconds so that the calibration value can be determined.

If you do not want to have the calibration value calculated every time, press the Calibratebutton. The calibration value is then determined from the data set to be specified and calibration level specified, entered in the Calibration value field, and the calibration mode changes to Fixed (in dB).

•You already know the calibration value in dB required for your microphone. Select Calibration fixed (in dB) and then specify the Calibration value directly in dB. A calibration value of 0 dB corresponds to a microphone sensitivity of 50 mV/Pa.

•You know the microphone sensitivity in mV/Pa from the calibration certificate. Select Calibration fixed (in mV/PA) and specify the microphone sensitivity directly in mV/Pa.

For more details, refer to Calibration in Acoustics.

Algorithm

There are three algorithms available for calculating the loudness.

The DIN 45692 and Bismarck methods differ only in the weighting function, which is used for calculating the sharpness. The specific loudness is calculated, weighted and added up according to ISO 532-1 (or DIN 45631). Both method only work for noise events with comparable loudness, since absolute loudness is ignored in the calculation.

This is remedied by the Aures algorithm is helpful here, where the absolute loudness influences the calculation result.

The results of the different methods therefore differ from each other greatly.

Normalization constant

The standard constant k for adjusting the calculated sharpness of the reference sound to 1 acum. The following applies: 0.105 ≤ k < 0.115. This value can be specified for the DIN 45692 procedure. This value is fixed for the other procedures.

Sound Field

The result depends on the particular sound field of the sound signal. You can specify whether the sound signal was measured in a free sound field or a diffuse sound field.

Time range to skip at the beginning

To calculate the sharpness of stationary sound signals, a time range can be removed at the beginning of the input signal. This is useful, for example, when the input signal contains a calibration measurement at the beginning. This value is ignored in the case of time-varying signals.

Observed Standards

FPScript Functions Used

AcousticCalibration

Loudness

SoundLevel

TimeDomainOctaveAnalysis

See Also

Acoustics Option

Analysis Objects

Calibration in Acoustics