Single‐Number Noise Rating for One‐Third Octave Band Sound Power Levels

1972 ◽  
Vol 52 (3A) ◽  
pp. 720-724 ◽  
Author(s):  
G. C. Maling ◽  
W. W. Lang
Keyword(s):  
Sound Power ◽  
Octave Band ◽  
Single Number

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.

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.

Analysis, Design And Simulation Of Piezoelectric Acoustic Microsensor

2012 ◽  
Author(s):  
Ahmad Kamal Ariffin Mohd Ihsan ◽  
Hock Aun Lim ◽  
Mohd Jailani Mohd Nor
Keyword(s):  
Piezoelectric Material ◽  
Hair Cells ◽  
Power Level ◽  
Outer Hair Cells ◽  
Sound Power ◽  
Octave Band ◽  
Quality Factors ◽  
Band Frequency ◽  
Cross Section Area ◽  
Half Power

Kertas kerja ini membentangkan reka bentuk analisis dan simulasi mikropenderia akustik piezoelektrik untuk meniru tiang-tiang rerambut dalam telinga manusia. Mikropenderia ini dikaji bagi membangunkan mikrofon baru. Bahan piezoelektrik PZT 5A digunakan sebagai tiangtiang rerambut atau rasuk dalam mikropenderia akustik piezoletrik. Analisis dijalankan menggunakan perisian FEMLAB bagi mengenal pasti panjang rasuk untuk mendapatkan frekuensi jalur oktaf dengan julat 31.5Hz dan 16kHz. Kemudian, perisian SIMULINK pula digunakan bagi menyelaku prestasi mikropenderia akustik. Luas keratan rentas rasuk ditetapkan 9 μm × 9 μm dan panjang pula berubah-ubah bagi mendapatkan pelbagai frekuensi salun. Panjang sesuai lebar jalur kuasa separuh dan faktor kualiti telah berjaya diperolehi menggunakan FEMLAB®. Prosedur penyelakuan telah dijalankan bagi mendapatkan aras kuasa bunyi bagi rasuk. Panjang rasuk, separuh kuasa lebar jalur, faktor kualiti dan kuasa bunyi merupakan parameter penting dalam mereka bentuk mikropenderia akustik. Kata kunci: Mikropenderia akustik, lebar jalur kuasa separuh, frekuensi jalur oktaf, bahan piezoletrik This paper presents the design analysis, and simulation of piezoelectric acoustic microsensor to imitate outer hair cells (OHCs) inside the human ear. This acoustic microsensor was utilised to develop a new type of microphone. Piezoelectric material PZT 5A was used as the hair cells or beams for the piezoelectric acoustic microsensor. The analysis was conducted using FEMLAB® software to identify the corresponding length to acquire the octave band frequency ranging from 31.5 Hz to 16 kHz. Furthermore, SIMULINK® software was employed to simulate the performance of the acoustic microsensor. The cross section area of the beams was kept at a constant value of 9 × 9 μm and their length was varied to acquire various resonant frequencies. The suitable lengths, the half power bandwidths and the quality factors of the beams were successfully obtained using FEMLAB®. The simulation procedure was undertaken to obtain sound power level of the beams. The length, half power bandwidth, quality factor and the sound power of the beams are important parameters in designing the acoustic microsensor. Key words: Acoustic microsensor, half power bandwidth, octave band frequency, piezoelectric material

Background subtraction in STEM energy-loss mapping

1984 ◽  
Vol 42 ◽  
pp. 568-569
Author(s):  
R.D. Leapman ◽  
K.E. Gorlen ◽  
C.R. Swyt
Keyword(s):  
Energy Loss ◽  
Signal To Noise Ratio ◽  
Statistical Error ◽  
Scanning Transmission Electron Microscope ◽  
Reference Image ◽  
Inverse Power Law ◽  
Transmission Electron ◽  
Least Squares Fit ◽  
Scanning Transmission ◽  
Single Number

The determination of elemental distributions by electron energy loss spectroscopy necessitates removal of the non-characteristic spectral background from a core-edge at each point in the image. In the scanning transmission electron microscope this is made possible by computer controlled data acquisition. Data may be processed by fitting the pre-edge counts, at two or more channels, to an inverse power law, AE-r, where A and r are parameters and E is energy loss. Processing may be performed in real-time so a single number is saved at each pixel. Detailed analysis, shows that the largest contribution to noise comes from statistical error in the least squares fit to the background. If the background shape remains constant over the entire image, the signal-to-noise ratio can be improved by fitting only one parameter. Such an assumption is generally implicit in subtraction of the “reference image” in energy selected micrographs recorded in the CTEM with a Castaing-Henry spectrometer.

Decay of Temporary Threshold Shift in Noise

1973 ◽  
Vol 16 (2) ◽  
pp. 267-270 ◽  
Author(s):  
John H. Mills ◽  
Seija A. Talo ◽  
Gloria S. Gordon
Keyword(s):  
Sound Field ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Octave Band ◽  
Band Noise ◽  
Lower Asymptote

Groups of monaural chinchillas trained in behavioral audiometry were exposed in a diffuse sound field to an octave-band noise centered at 4.0 k Hz. The growth of temporary threshold shift (TTS) at 5.7 k Hz from zero to an asymptote (TTS ∞ ) required about 24 hours, and the growth of TTS at 5.7 k Hz from an asymptote to a higher asymptote, about 12–24 hours. TTS ∞ can be described by the equation TTS ∞ = 1.6(SPL-A) where A = 47. These results are consistent with those previously reported in this journal by Carder and Miller and Mills and Talo. Whereas the decay of TTS ∞ to zero required about three days, the decay of TTS ∞ to a lower TTS ∞ required about three to seven days. The decay of TTS ∞ in noise, therefore, appears to require slightly more time than the decay of TTS ∞ in the quiet. However, for a given level of noise, the magnitude of TTS ∞ is the same regardless of whether the TTS asymptote is approached from zero, from a lower asymptote, or from a higher asymptote.

Active control of compressor noise in the machinery room of refrigerators

2019 ◽  
Vol 67 (5) ◽  
pp. 350-362
Author(s):  
J. M. Ku ◽  
W. B. Jeong ◽  
C. Hong
Keyword(s):  
Control System ◽  
Active Control ◽  
Weighting Function ◽  
Reference Signal ◽  
Active Noise Control ◽  
Dominant Frequency ◽  
Time Signal ◽  
Frequency Noise ◽  
Sound Power ◽  
Fxlms Algorithm

The low-frequency noise generated by the vibration of the compressor in the machinery room of refrigerators is considered as annoying sound. Active noise control is used to reduce this noise without any change in the design of the compressor in the machinery room. In configuring the control system, various signals are measured and analyzed to select the reference signal that best represents the compressor noise. As the space inside the machinery room is small, the size of a speaker is limited, and the magnitude of the controller transfer function is designed to be small at low frequencies, the controller uses FIR filter structure converged by the FxLMS algorithm using the pre-measured time signal. To manage the convergence speed for each frequency, the frequency-weighting function is applied to FxLMS algorithm. A series of measurements are performed to design the controller and to evaluate the control performance. After the control, the sound power transmitted by the refrigerator is reduced by 9 dB at the first dominant frequency (408 Hz in this case) and 3 dB at the second dominant frequency (459 Hz here), and the overall sound power decreases by 2.6 dB. Through this study, an active control system for the noise generated by refrigerator compressors is established.

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