An Investigation of the Perception Thresholds of Band-Limited Low Frequency Noises: Influence of Bandwidth

2003 ◽  
Vol 22 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Yasunao Matsumoto ◽  
Yukio Takahashi ◽  
Setsuo Maeda ◽  
Hiroki Yamaguchi ◽  
Kazuhiro Yamada ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Frequency Range ◽  
Pass Filter ◽  
Sound Pressure Levels ◽  
Pure Tones ◽  
Band Limited ◽  
The One ◽  
Frequency Weighting ◽  
40 Hz

Perception thresholds of complex low frequency noises have been investigated in a laboratory experiment. Sound pressure levels that were just perceptible by subjects were measured for three complex noises and three pure tones. The complex noises had a flat constant spectrum over the frequency range 2 to 10, 20, or 40 Hz and decreased at 15 dB per octave at higher frequencies. The frequencies of the pure tones used in this study were 10, 20 and 40 Hz. The perception thresholds were obtained using an all-pass filter, one-third octave band filters, and the G frequency weighting defined in ISO 7196. The G-weighted sound pressure levels obtained were compared with 100 dB which is described in ISO 7196 as the G-weighted level corresponding to the threshold of sounds in the frequency range 1 to 20 Hz. The perception thresholds of the pure tones measured in this study were comparable to the results available in various previous studies. The one-third octave sound pressure levels obtained for the thresholds of the complex noises appeared to be lower than the measured thresholds of the pure tones. The G-weighted sound pressure levels obtained for the thresholds of the complex noises appeared to be lower than 100 dB.

Study of Sound Insulation of Control Cabins in Industry in the Low Frequency Range

1992 ◽  
Vol 11 (2) ◽  
pp. 42-46
Author(s):  
Anna Kaczmarska ◽  
Danuta Augustyriska
Keyword(s):  
Noise Reduction ◽  
Sound Pressure ◽  
Low Frequency ◽  
Machine Building ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Sound Pressure Levels ◽  
Lower Frequencies

The number of control cabins installed in industry has increased considerably during the last few years. Most cabins installed nowadays show a satisfactory noise reduction in the frequency range above 500 Hz. The effect of noise damping however shows a gradual decrease for lower frequencies. The present paper is a description of the distribution of low frequency noise in different types of control cabins installed in typical low frequency noise environments in steel plants and the machine building industry. Measurements were made in 20 control cabins, constructed of metal and stone Measurements of sound pressure levels in octave bands were made inside and outside the cabins. The sound pressure level in octave bands in the low frequency range (4–31.5 Hz) inside the cabins was high and varied between 60–108 dB. This is probably due to the insufficient noise reduction for lower frequencies. In some control cabins there was an increased level of low frequency noise inside the cabin compared to the outside. In these control cabins sound pressure levels exceed the admissible values according to Polish standards. The increase of noise level within the low frequency range is considered to be based on resonances.

Thresholds and Acceptability of Low Frequency Pure Tones by Sufferers

2005 ◽  
Vol 24 (3) ◽  
pp. 163-169 ◽  
Author(s):  
Yukio Inukai ◽  
Hideto Taya ◽  
Shinji Yamada
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Psychophysical Method ◽  
Psychophysical Experiment ◽  
Living Room ◽  
Sensory Thresholds ◽  
Low Frequencies ◽  
Sound Pressure Levels ◽  
Measurement Experiment ◽  
Pure Tones

In order to investigate sensory thresholds and to make subjective evaluations of low frequency pure tones in noise sufferers who complain of annoying environments in their everyday life, sound pressure levels of sensory thresholds and subjectively acceptable maximum SPL levels for a living room were measured in a low frequency chamber. These measurements involved a psychophysical experiment using eleven pure tones at low frequencies from 10Hz to 100 Hz as stimuli, and the psychophysical method of subject adjustment was used for the measurements. Twelve members of the noise-sufferer's society in Japan participated as subjects (referred to as participants in the measurement experiment). The results show that all the participants' acceptable maximum sound pressure levels were relatively low, and nearly equal to their sensory thresholds. These results are characteristic of the participants and differ from the previous results obtained from the other adults.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Annoyance of Low Frequency Tones and Objective Evaluation Methods

2005 ◽  
Vol 24 (2) ◽  
pp. 81-95 ◽  
Author(s):  
Jishnu K. Subedi ◽  
Hiroki Yamaguchi ◽  
Yasunao Matsumoto ◽  
Mitsutaka Ishihara
Keyword(s):  
Sound Pressure ◽  
Hearing Threshold ◽  
Low Frequency ◽  
Objective Evaluation ◽  
Evaluation Methods ◽  
Frequency Separation ◽  
Rate Of Increase ◽  
Pure Tones ◽  
Four Levels ◽  
Loudness Model

Annoyance of low frequency pure and combined tones was measured in a laboratory experiment. Three low frequency tones at frequencies of 31.5, 50 and 80 Hz at four sound pressure levels, from about 6 dB to 24 dB above average hearing threshold, were selected as pure tones. The combined tones were combinations of two tones: the four levels of 31.5, 50 and 80 Hz tones and a constant level 40 Hz tone. The results showed that the rate of increase in annoyance of pure tones with increase in the sound pressure level was higher at lower frequencies, as reported in previous studies. The results for the combined tones showed that the increase in the annoyance of the combined tone compared to the annoyance of pure tone was dependent on the level difference of the two tones and their frequency separation. These results were compared with the evaluation obtained from different objective methods. The three methods were Moore's loudness model, the low frequency A-weighting and the total energy summation used as objective evaluation methods. Among the methods, the low frequency A-weighting gave the best correlation.

Gyro Rock Crusher and Asphalt Plant Sound Power Levels

2012 ◽  
Author(s):  
Henry A. Scarton ◽  
Kyle R. Wilt
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Sound Power ◽  
Far Field ◽  
Atmospheric Attenuation ◽  
Frequency Sound ◽  
Sound Pressure Levels ◽  
Rock Crusher

Sound power levels including the distribution into octaves from a large 149 kW (200 horsepower) gyro rock crusher and separate asphalt plant are presented. These NIST-traceable data are needed for estimating sound pressure levels at large distances (such as occurs on adjoining property to a quarry) where atmospheric attenuation may be significant for the higher frequencies. Included are examples of the computed A-weighted sound pressure levels at a distance from the source, including atmospheric attenuation. Substantial low-frequency sound power levels are noted which are greatly reduced in the far-field A-weighted sound pressure level calculations.

scholarly journals Noise-silencing technology for upright venting pipe jet noise

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879481 ◽  
Author(s):  
Enbin Liu ◽  
Shanbi Peng ◽  
Tiaowei Yang
Keyword(s):  
Natural Gas ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Frequency Range ◽  
Expansion Chamber

When a natural gas transmission and distribution station performs a planned or emergency venting operation, the jet noise produced by the natural gas venting pipe can have an intensity as high as 110 dB, thereby severely affecting the production and living environment. Jet noise produced by venting pipes is a type of aerodynamic noise. This study investigates the mechanism that produces the jet noise and the radiative characteristics of jet noise using a computational fluid dynamics method that combines large eddy simulation with the Ffowcs Williams–Hawkings acoustic analogy theory. The analysis results show that the sound pressure level of jet noise is relatively high, with a maximum level of 115 dB in the low-frequency range (0–1000 Hz), and the sound pressure level is approximately the average level in the frequency range of 1000–4000 Hz. In addition, the maximum and average sound pressure levels of the noise at the same monitoring point both slightly decrease, and the frequency of the occurrence of a maximum sound pressure level decreases as the Mach number at the outlet of the venting pipe increases. An increase in the flow rate can result in a shift from low-frequency to high-frequency noise. Subsequently, this study includes a design of an expansion-chamber muffler that reduces the jet noise produced by venting pipes and an analysis of its effectiveness in reducing noise. The results show that the expansion-chamber muffler designed in this study can effectively reduce jet noise by 10–40 dB and, thus, achieve effective noise prevention and control.

Effects of Very Low Frequency Tones on Auditory Thresholds

1966 ◽  
Vol 9 (1) ◽  
pp. 150-160 ◽  
Author(s):  
J. Jerger ◽  
B. Alford ◽  
A. Coats ◽  
B. French
Keyword(s):  
Adverse Effects ◽  
Sound Pressure ◽  
Human Subjects ◽  
Low Frequency ◽  
Pressure Level ◽  
Variable Speed ◽  
Frequency Range ◽  
Auditory Thresholds ◽  
Very Low Frequency ◽  
Piston Cylinder

Nineteen human subjects were exposed to repeated three-minute tones in the sound pressure level range from 119 to 144 dB and the frequency range from 2–22 cps. The tones were produced in an acoustic test booth by a piston-cylinder arrangement, driven by a variable speed direct current motor. Eight subjects showed no adverse effects. Temporary threshold shifts (TTS) of 10 to 22 dB in the frequency range from 3 000 to 8 000 cps were observed in the remaining 11 subjects. In addition, the 7 and 12 cps signals produced considerable masking over the frequency range from 100 to 4 000 cps.

Comparison of Seven Systems for High-Frequency Air-Conduction Audiometry

1970 ◽  
Vol 13 (2) ◽  
pp. 254-270 ◽  
Author(s):  
Cecil K. Myers ◽  
J. Donald Harris
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Frequency Noise ◽  
Noise Band ◽  
Frequency Range ◽  
Pure Tones ◽  
Auditory Acuity ◽  
Narrow Bands ◽  
Reference Threshold ◽  
Air Conduction

Seven equipment systems were assembled to examine human auditory acuity from 8 to 20 kHz. Two loudspeakers and two earphones were examined, together with two types of stimulus (pure tones and narrow bands of noise) and two psychometric methods (Limits and Adjustments). All systems were capable of providing usably reliable thresholds on 28 ears throughout the whole frequency range. When carefully calibrated, several systems (those involving loudspeakers, as well as those involving earphones) yielded comparable reference threshold sound-pressure levels at the eardrum. A preference was expressed for a system using Bekesy threshold tracking with a changing-frequency noise band of 300 Hz, and for a discrete-tone system using the Method of Constants.

Sign in / Sign up

Export Citation Format

Share Document