Skip to content

Select your region & language

Global

Region

O-Solution Sound Quality Evaluation Function OS-0525

Sound quality evaluation that takes into account human hearing characteristics

Generally, sound countermeasures and evaluations for equipment are based on sound pressure levels, FFT analysis, 1/3 octave analysis, and other methods.
However, such analyses do not adequately consider the characteristics of human hearing, and the same results may result in different listening impressions.
Furthermore, when people hear sounds, they experience various sensations related to the sound, such as "loudness," "sharpness," and "roughness."
The OS-0525 sound quality evaluation function takes into account the characteristics of human hearing and can determine sound quality evaluation indices that correspond to various perceptions of sound.

Supported standards

  • Stationary sound loudness (ISO 532-1)

  • Non-stationary sound loudness (ISO 532-1)

  • TNR/PR(ISO7779 Annex D)

Sound quality evaluation metrics

  • Loudness [sound level]

  • Sharpness [instep height]

  • Tonality [pure pitch]

  • Roughness [cloudiness]

  • Fluctuation intensity [perceived fluctuation]

  • TNR/PR [discrete pure tone]

  • CI(comfort index)※

*This is one of the sound evaluation metrics developed by Professor Sonoko Kuwano*, and is a value obtained by adding "sharpness value" and "1/10 of the A-weighted time-averaged sound level". There are good examples of correlation with the unpleasantness of environmental noise and machine noise. The scope of application is still being studied, so please use it as a reference value.

Sonoko Kuwano* (Doctor of Engineering) Professor Emeritus, Osaka University. Former President of the Acoustical Society of Japan, Vice President of the Japan Society of Noise Control Engineering, and Vice President of the International Acoustical Society.

Examples of analysis for 6 machine sounds

Loudness is No. 1

What is loudness?

Loudness refers to a subjectively perceived intensity of sound (the sum of the excitation levels of the auditory nerves). A pure tone of 1 kHz at 40 dB is defined as 1, and other sounds are expressed as multiples of this value. The unit is the sone.

  • Loudness is No. 2
  • Loudness is No. 3

Sound Quality Evaluation Examples: Comparison of Machine Sounds

The diagram below shows an example of analysis for six machine sounds with different loudness levels. The left diagram (blue) shows the results of analysis using A-weighted sound pressure level (noise level), where all six sounds show the same value. In contrast, the right diagram (red) shows the results of analysis using "loudness," a quantity that indicates the loudness of a sound, and the differences between the six sounds are evident. When we actually listen to these sounds, they sound different in loudness, just as shown in the loudness results below. By using loudness, we can evaluate the differences in loudness as heard by humans, which cannot be evaluated using only quantities based on sound pressure, such as A-weighted sound pressure level.

Model name Product name quantity
OS-5100 Platform 1
OS-0525 Sound quality evaluation function 1

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

*Sound will play. Please adjust your volume accordingly.

  • Sound Quality Evaluation Examples: Comparison of Machine Sounds

Sound Quality Evaluation Example: Unseen Noise Becomes Visible

If time-varying noise occurs before the engine warms up, but disappears after the engine has warmed up, then performing a fluctuation intensity analysis focusing on the time-varying component can reveal the true nature of the noise that was not visible in the octave analysis.

Model name Product name quantity
OS-5100 Platform 1
OS-0524 Octave analysis function 1
OS-0525 Sound quality evaluation function 1

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

  • Sound Quality Evaluation Case Study: Uncovering previously invisible noise No. 1

Before warming up (when the engine is cold)

After warming up (when the engine is warm)

  • Sound Quality Evaluation Case Study: Uncovering previously invisible noise No. 2
  • Sound Quality Evaluation Case Study: Uncovering previously invisible noise No. 3

Sound Quality Evaluation Example: Comparison of Excavator Sound and Symphony Sound

Sound Quality Evaluation Example: Comparison of Excavator Sound and Symphony Sound No. 1

We will compare the sound of an excavator with a symphony (from the fourth movement of Beethoven's Symphony No. 5). These two sounds are completely different, but if we perform a 1/3 octave analysis, which is commonly used to evaluate sound, the spectra will be almost identical, as shown in the data below. Therefore, we will use roughness, a parameter that represents the roughness of sound, to compare and evaluate these two sounds. A higher value indicates greater "roughness" of the sound, and we can clearly capture the difference between the sound of the symphony and the sound of the excavator by the difference in "roughness".

Model name Product name quantity
OS-5100 Platform 1
OS-0524 Octave analysis function 1
OS-0525 Sound quality evaluation function 1

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

Excavator

Symphony

  • Sound Quality Evaluation Example: Comparison of Excavator Sound and Symphony Sound No. 2
  • Sound Quality Evaluation Case Study: Comparison of Excavator Sound and Symphony Sound No. 3

Sound Quality Evaluation Example: Motor Noise Evaluation

Sounds generated by motors and inverters contain pure tone components, making them easily perceived as irritating even at small amplitudes. Indicators for quantifying pure tone perception include tonality, TNR (Tone-to-Noise Ratio), and PR (Prominence Ratio). By analyzing TNR and PR, the frequencies of problematic pure tone components can be identified. Below is an example of the results of analyzing tonality and PR. Comparing the tonality and PR of two motors, one with a noticeable "beeping" noise and the other with an improved noise, we find that even though the sound pressure levels are the same, the tonality and Total-PR (sum of PR) values of the defective product are higher, indicating a higher degree of pure tone.
The PR graph allows you to check the PR values and frequencies of the prominent pure tone components in defective products. You can also check whether the PR values exceed the criteria for prominent discrete pure tones in ISO 7779 Annex D.

  Sound pressure level tonality Total-PR
■NG 67.5dB 0.9 tu 16.8dB
■Improved product 66.5dB 0.5 tu 11dB

NG item

Improved product

*Sound will play. Please adjust your volume accordingly.

  • Sound Quality Evaluation Example: Motor Noise Evaluation