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O-Solution Variable Sound Analysis Function OS-0526

There are many sounds in the world that are "annoying" even though they are not particularly loud. For example, the rattling and buzzing sounds that are sometimes heard from interior parts of a car while driving, or the buzzing noise that mixes with the rotation sound of a small motor. There are several reasons why these sounds are "annoying," but sounds that show significant temporal fluctuations are often perceived as irritating even if their volume (level) is not very high. Fluctuation sound analysis is an analysis that can extract only the components with large temporal fluctuations that are not affected by the level. This makes it possible to quantify various temporal fluctuation characteristics that were difficult to detect with conventional FFT, basic roughness, and fluctuation intensity. In addition, it is possible to evaluate various sound designs (flavoring) on two axes: timbre (pitch) and temporal fluctuation period, enabling deeper analysis than conventional techniques.

Transmission gear rattling noise
Small motor making abnormal noise (buzzing)
Engine intake and exhaust sound (rumbling)
Refrigerator compressor operating sound (beeping)

The fluctuating sound simulator allows you to adjust and evaluate sound by removing unwanted fluctuating components or emphasizing easily audible ones while reviewing the fluctuating sound analysis results. Conventional methods using band reject filters to remove fluctuating components attenuate not only the fluctuating sound but also the components in that frequency band. However, the fluctuating sound simulator allows you to remove, emphasize, or extract only the fluctuating sound while largely preserving the frequency characteristics.

Here, we compare the frequency characteristics when the fluctuating component is removed using a fluctuating sound simulator and the conventional band reject filter method. In both cases, the rattling sound is no longer audible. However, while the frequency characteristics hardly changed from the original signal when using the fluctuating sound simulator, when using the band reject filter, the frequency characteristics changed considerably because the component in the relevant band was attenuated and removed.

Frequency characteristics after noise reduction using a fluctuating sound simulator.
Frequency characteristics after removal using a band reject filter

Small motor making abnormal noise (buzzing)

Previously, people judged the quality of small motors by listening to their operating sounds. Frequency analysis was attempted to enable numerical judgment, but it was pass/fail judgment. By performing a fluctuating sound analysis focusing on the fluctuations in the sound, the difference between good and defective products became clear.

Model name	Product name	quantity
OS-5100	Platform	1
OS-0522	FFT analysis function	1
OS-0526	Fluctuation sound analysis function	1

*A sound recording device (such as a high-performance sound level meter or FFT analyzer) is required.

img-o-solution-os0526-01 — Transmission gear rattling noise

The timbre of gear teeth rattling has components in the 800 Hz band, but in FFT analysis, the rattling sound is buried in the background noise level, making it impossible to find its features. In "fluctuation sound analysis," the values in the cells of the 800 Hz band (vertical axis) as the timbre of the sound and the 20 Hz band (horizontal axis) as the fluctuation period are increased. This makes it possible to represent sounds whose features cannot be extracted at all by sound intensity alone.