Measuring the sound power of a noise source and detecting pure tones with a single instrument combining true 1/3 octave band digital filters and an FFT analyzer

1987 ◽  
Vol 82 (S1) ◽  
pp. S113-S113
Author(s):  
Ole‐Herman Bjor ◽  
Gustav Ese
Keyword(s):  
Digital Filters ◽  
Noise Source ◽  
Sound Power ◽  
Octave Band ◽  
Pure Tones ◽  
Single Instrument

Sound Power Assessment, Noise Source Identification and Directivity Analysis of Compaction Machines

2021 ◽  
Author(s):  
Milind Dadarao Kandalkar ◽  
Jaykumar bari ◽  
Dhondiram Mole ◽  
Nagesh Harishchandra Walke
Keyword(s):  
Source Identification ◽  
Noise Source ◽  
Sound Power ◽  
Noise Source Identification

Masking of Auditory Responses in the Medulla Oblongata of Goldfish

1973 ◽  
Vol 59 (2) ◽  
pp. 415-424
Author(s):  
PER S. ENGER
Keyword(s):  
White Noise ◽  
Background Noise ◽  
Nervous Activity ◽  
Band Width ◽  
Masking Effect ◽  
Noise Band ◽  
Octave Band ◽  
Tone Frequency ◽  
Centre Frequency ◽  
Pure Tones

1. The nervous activity of single auditory neurones in goldfish brain have been measured. 2. Four types of acoustic stimuli were used, (1) pure tones, (2) noise of one-third octave band width, (3) noise of one-octave band width with centre frequency equal to the pure tone, and (4) white noise. 3. Except for white noise, these stimuli produced the same response to equal sound pressures. The white noise response was less, presumably because the frequency range covered by a single neurone is far narrower than the range of white noise. 4. The conclusion has been reached that for low-frequency acoustic signals, the acoustic power over a frequency band of one to two octaves is integrated by the nervous system. 5. The masking effect of background noise on the acoustic threshold of single units to pure tones is strongest when the noise band has the same centre frequency as the test tone. In this case the tone threshold increases linearly with the background noise level. 6. When the noise band was centred at a different frequency from the tone, the masking effect decreased at a rate of 20-22 dB/octave for the first one-third octave for a tone frequency of 250 Hz. For a tone of 500 Hz the masking effect of lower frequencies was stronger and was reduced by only some 9 dB/octave for the first one-third octave.

Statistical assessment of A-weighted sound power level for printer with electrophotographic engine

2021 ◽  
Vol 263 (6) ◽  
pp. 936-941
Author(s):  
Kohei Shimoda
Keyword(s):  
Power Level ◽  
Sound Power ◽  
Octave Band ◽  
Reference Distribution ◽  
Limit Value ◽  
Upper Limit ◽  
Sound Power Level ◽  
Standard Distribution ◽  
Noise Test ◽  
Better Than

Statistical distribution and statistical upper limit (the value which 93.5 % of the batch of new equipment are expected to lie) of A-weighted sound power level for one office printer were experimentally estimated from 10 new samples picked up from market. The printer is capable of A4-size printing with electrophotographic engine which corresponds Annex C.16 Page printers in ECMA74 17th (2019). A-weighted sound power level for continuous printing mode was determined in accordance with noise test code for ITTE (Information Technology and Telecommunications Equipment such as printers and personal computers), ISO 7779:2018 and ECMA-74 Annex C. Sample standard distribution of production of overall A-weighted sound power level (determined from 100-10000 Hz one-third-octave band) is 0.25 dB, whereas individual one-third-octave band has larger distribution. The value obtained is better than reference distribution 1.32 dB set in ISO 9296:2017 which states estimation of statistical upper limit value of the batch of equipment for ITTE.

Identification of the Vehicle Noise Source by Sound Intensity Method

2011 ◽  
Vol 346 ◽  
pp. 634-638 ◽  
Author(s):  
He Li ◽  
Qing Rong Zhao ◽  
Bang Chun Wen
Keyword(s):  
Power Spectrum ◽  
Noise Source ◽  
Sound Intensity ◽  
Regulation System ◽  
Sound Power ◽  
Analysis Software ◽  
Noise Sources ◽  
Vehicle Noise ◽  
Measurement Results ◽  
Radiation Noise

In this paper, we analysed the level of radiation noise and distribution of noise sources of car’s engine and front panels by using sound intensity method. To get the nephogram of sound intensity and sound power spectrum, we used the sound intensity probe and Multi-channel Data Acquisition Regulation System B&K 3560-D and Pulse Data Processing Analysis Software. By analysing experimental results, we can conclude the location of noise sources of these parts. The measurement results will serve as a reference for the car noise reduction.

Analysis of the Sound Power Level Emitted by Portable Electric Generators (Outdoor Powered Equipment) Depending on Location and Measuring Surface

2013 ◽  
Vol 430 ◽  
pp. 266-275 ◽  
Author(s):  
Elena Postelnicu ◽  
Valentin Vladut ◽  
Cristian Sorica ◽  
Petru Cardei ◽  
Ion Grigore
Keyword(s):  
Noise Source ◽  
Power Level ◽  
Acoustic Power ◽  
Sound Power ◽  
Noise Emission ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Measurement Surface ◽  
Electric Generators

Acoustic power is a measure which must be specified on the outdoor used equipments and its determination depends on several factors: the place where the equipment works (indoor or outdoor), the placement of the microphones for its determination (the distance less or greater from the noise source), the shape of the measurement surface (parallelepiped or hemispherical). This paper aims to analyze the values obtained in these situations and interpret the data to determine the influence that each factor has on the acoustic power compared with the values obtained (permissible) according to Directive regarding noise emission D 2000/14/EC.

One Stage and Two Stage Vibration Isolators as Applied to High Speed Textile Spindles to Achieve Noise Reduction

1978 ◽  
Vol 100 (1) ◽  
pp. 33-40 ◽  
Author(s):  
L. W. Foster
Keyword(s):  
Low Noise ◽  
Single Stage ◽  
Sound Power ◽  
Octave Band ◽  
Noise Levels ◽  
Two Stage ◽  
Noise And Vibration ◽  
Vibration Isolators ◽  
One Stage ◽  
The Impact

The operation of ring spinning frames in textile mills can create spinning room noise levels of 90 to 95 dBA. The spindle bobbin mechanisms (generally 300 to 400 per machine) which are operated at spindle speeds of 6,000 to 14,000 rpm are major sources of noise in this type of machinery. The rotating unbalance force in the spindle-bobbin mechanism creates high frequency vibrations in the spindle blade and in the spindle bolster which contains the bearings on which the blade rotates. The vibrations generated by the spindle bobbin mechanism and the bearings are transmitted through the spindle bolster to the rail structure of the spinning frame where they cause sand energy to be radiated. This paper describes the use of two types of elastomeric vibration isolators located between the spindle bolster and the rail to achieve reductions of vibration and noise levels associated with the spindle-bobbin-rail subsystem of spinning frames. The two types of elastomeric isolators employed are: (1) a single-stage isolator where a bonded elastomeric mounting of annular design is placed between the bolster and the rail, and (2) a two-stage isolator which incorporates an annular intermediate mass element between two annular elastomeric sections that provide the interfaces to the spindle and to the rail. The two stage isolator is a novel design for rotating spindle type applications and employs the classical two stage isolator principle to achieve greater attenuation of vibrations. While it has been known for some time that single stage elastomeric isolators provide an effective means of reducing vibrations and noise in textile spinning and twisting machines, recent emphasis on reducing machine noise levels has motivated increased effort to better describe and apply elastomeric isolators. The two-stage isolator concept has been employed in an attempt to achieve higher operating speeds and, therefore, higher productivity while keeping noise levels within acceptable limits. In order to demonstrate the degrees of noise and vibration reductions that can be attained using the two types of isolators in comparison with the non-isolated or hard-mounted spindle, tests were performed using a single oil base type spinning spindle with a full bobbin. The spindle-bobbin mechanism was mounted to a representative rail by the three mounting methods described previously and operated at speeds of 11,000 rpm and 14,000 rpm in a reverberation room. Octave band sound power level measurements and one-tenth octave band sound pressure measurements were made to compare the performance of the mounting methods. These measurements were made using six microphones at different locations and sampling their output signals at a high rate over an extended interval of time. One-tenth octave horizontal and vertical rail acceleration responses were obtained concurrently with the noise responses. These noise and vibration responses are presented and discussed in the paper. The results show that the elastomeric isolators provide significant reductions in rail vibration response levels in the spindle bearing vibration frequency range of 500 to 2000 Hz. The corresponding overall sound power levels for the two operating speeds when using one stage isolators were 8 to 18 dBA below the hard-mounted spindle condition. When using the two-stage isolator, the overall sound power levels for the two operating speeds were 9 and 20 dBA below the hard mounted spindle condition. The results demonstrate the importance of properly designing the mounting to tune the system for low noise responses while minimizing the impact on other operatonal criteria such as spindle static deflection and dynamic motion. A discussion of the isolator design parameter trade-offs is presented along with comments regarding the limitations of the testing and the constraints involved in predicting the noise level reduction to be expected for a whole spinning frame.

scholarly journals COGENERATION UNIT NOISE REDUCTION BY ITS CASE

2021 ◽  
Vol 2021 (2) ◽  
pp. 4501-4504
Author(s):  
RADEK STRAMBERSKY ◽  
◽  
VACLAV PAVELKA ◽  
TOMAS PAWLENKA ◽  
PAVEL SURANEK ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Frequency Spectrum ◽  
Noise Source ◽  
Microphone Array ◽  
Noise Measurement ◽  
Sound Power ◽  
Final Number ◽  
Beamforming Algorithm

This paper deals with cogeneration unit noise measurement by the acoustic camera. Noise is not only measured as the final number of sound power levels, but also its original location is determined with the use of the beamforming algorithm. The properties of the used microphone array are considered and numerically calculated as every different microphone array layout will measure with another resolution. From the frequency spectrum, the possible technical source is determined. The results of noise source visualization show the cogeneration unit case noise decreasing effect while also offering the possibilities for design improvements.

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