Technical Report

Why we measure fluctuation sound

Although the magnitude of the sound is not so large, there are many “unpleasant sound”.
For example, “rattling” and “humming“ sounds generated from interior items while driving a car, etc. Sounds that have significant temporal fluctuation often feel unpleasant even its magnitude (level) is not so large.

Fluctuation sound analysis enables to quantify the characteristics of various temporal fluctuations that were difficult to detect with conventional FFT, basic roughness or fluctuation strength.

Analysis example
-Abnormal sound of small motor-

Very high-frequency noise may be generated due to motor current abnormality. Record the motor sound to an SD memory card in the LA-7500 sound level meter. By using the OS-2760 Fluctuation Sound Analysis package, you can see that only NG products have large fluctuations in high-frequency components (8 to 10 kHz) as following figure. This component is the cause of abnormal noise, and if you observe this band (frequency: 10 kHz, fluctuation frequency: 60 Hz), it is possible to judge OK or NG of the product.

Example of System Configuration

1. OS-2760 Fluctuation Sound Analysis package*

2. LA-7500 High performance Sound Level Meter

3. LA-0704 Sound recording function

4. SC-2500 Sound Calibrator

*PC for sound analysis software should be prepared by customers.

2019 Exhibition Schedules (From April to June)

China

Date	Name	Place	Exhibit	Organizer
May 23-24	Denkei Testing Exhibition 2019 in Tianjin	The Westin Tianjin	Sound and Vibration analysis instruments	DENKEI TRADING (SHANGHAI) CO.,LTD.

Spain

Date	Name	Place	Exhibit	Organizer
Jun 16-19	Inter-Noise 2019	Palacio Municipal de Congresos de Madrid, SPAIN	Sound and Vibration analysis instruments	Sociedad Española de Acústica (SEA)

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