This content is not included in your SAE MOBILUS subscription, or you are not logged in.
A Plea for Linear Units as an Alternative to Decibels and Octaves
ISSN: 0148-7191, e-ISSN: 2688-3627
Published May 16, 2005 by SAE International in United States
Annotation ability available
Decibels were originally developed in the 1920s by the telephone industry (AT&T and Bell Labs). Initially the unit was the bel, derived from the name of Bell Labs and defined as the logarithm to the base 10 of the transmission loss of electrical power in telephone lines. It was also used for voice signals in telephones where the preferred unit became a tenth of a bel or decibel. The adoption of decibel for sound appears to be due principally to the dominant position of the Bell's acoustical research staff in the 1920s and 1930s. Octaves have their origin in music and were used to facilitate the use of analogue filters in partitioning the frequency scale. Partitioning into octaves divides the frequency scale into bands increasing in width by a factor of 2 with increasing frequency. To obtain greater resolution, the partitioning is often performed in 1/3 and sometimes in 1/12 octaves. However resolution remains poor particularly at higher frequencies. The ear can distinguish frequency differences that are much smaller than 1/3 or 1/12 octaves. Decibels and octave filtering originated in an era when slide rules and logarithmic tables were used for engineering computation. Nowadays digital signal processing with Fourier transforms provides much better resolution. Measurements are made in ordinary linear SI units followed by conversion into decibels and octaves. This final step is unnecessary. The data would be simpler and more informative if left in the linear SI form. Octaves and their fractions obscure frequency information. In some applications involving the measurement of vector quantities, such as sound power flow (intensity), the use of decibels and octave filtering is a definite impediment to the measurement. In this paper these questions are explored in detail. Also sound-power testing is proposed as an alternative to passby and other forms of noise testing in the auto industry. The benefits of sound-power testing are (a) it is independent of the test site and (b) it provides information identifying and quantifying the contributions of component noise sources.
|Technical Paper||Analytical Predictions for the Chain Drive System Resonance|
|Technical Paper||Accuracy and Limitations of Using an iOS Device for Noise and Vibration Measurements|
|Technical Paper||Acoustical Analysis of Composite Materials|
CitationHickling, R., "A Plea for Linear Units as an Alternative to Decibels and Octaves," SAE Technical Paper 2005-01-2549, 2005, https://doi.org/10.4271/2005-01-2549.
- Fahy F. J. “Sound Intensity” E&FN Spon, Chapman and Hall London 1995
- Clay C. S. Munk W. H. “Underwater Sound Transmission and SI Units” ECHOES Acoust. Soc. Amer. 1998
- Hickling R Brown R. L. “Analysis of acoustic communication by ants” Journ. Acoust. Soc. Amer. 108 4 1920 1929 2000
- Masden K. R. “Noise Measurents and the dB” Royal Aircraft Establishment Farnborough, England 1980
- Pierce A. D. “Acoustics: An Introduction to its Physical Principles and Applications” 57 59 Acoustical Society of America Woodbury New York 1989
- American National Standard “Preferred Frequencies and Band Numbers for Acoustical Measurements” American National Standards Institute New York 1976
- Chung J. Y. “Cross-spectral method of measuring acoustic intensity” General Motors Research Laboratories Warren, MI 1977
- Elko G. W. “Frequency Domain Estimation of the Complex Acoustic Intensity and Acoustic Energy Density” Pennsylvania State University 1984
- Hickling R. Lee P. “Determining Sound Power in Reverberation Rooms and Other Indoor Work Spaces using Vector Sound-Intensity Measurement” Proceedings NOISE-CON 97 1997
- Hickling R. Bolen L. N. Schumacher R. F. “Indoor System for Efficient Measurement of the SOUND Power of Light Vehicles and for Noise-Control Diagnostics” SAE Paper 891145 , P-222, Proceedings of Noise and Vibration Conference 1989
- Hickling R. Lee P. Wei W. “Investigation of Integration Accuracy of Sound Power Measurement using an Automated Sound-Intensity System” Applied Acoustics 1996
- Pope J. Hickling R. Feldmaier D. A. Blaser D. A. “The use of acoustic intensity scans for sound power measurement and noise source identification in surface transportation vehicles” SAE Paper No. 810401 , SAE Transactions 1981
- ““Determination of sound power levels of noise sources using sound intensity, Part I. Measurement at discrete points” International Organization for Standardization Geneva, Switzerland 1992
- “Engineering method for determination of sound power levels of noise sources using sound intensity” American National Standards Institute New York 1992