Effective Sound Pressure Research Articles

GIS UNTUK PEMETAAN KEBISINGAN MENGGUNAKAN CLASSIFIER MODEL

Noise is an undesirable sound from a business or activity in a certain level and time that can cause public health problems and environmental comfort. Noise occurs because there is a noisy source, a material delivery medium or air. The impact of noise in an area is of great influence to the health and well-being of people, animals and wildlife and disturbance to the natural ecosystem. For human health, noise can cause disturbances in the system of hearing and digestion, stress, headache, increased blood pressure and can reduce performance. Equipment used to conduct this research one of them is the Sound Level Meter which is the main tool in noise research. This tool is downloaded from the playstore app. SLM is used to measure noise intensity. The SLM used is a digital SLM capable of measuring effective sound pressure levels in decibels (dB). This tool measures noise with a scale between 30 ~ 100 dB. This research used qualitative method by conducting survey to Jl KH. Noer Ali West Bekasi to Jl. Wisma Asri Park Bekasi Utara. In this study using GIS with data collection method using Data Mining in Hierarchical clustering.

20907 吸音材を内部に持つヘルムホルツ共鳴器による騒音低減

Helmholtz resonator is a device for noise reduction. It is effective for noise that has a dominant frequency component. However, in some other frequency components, Helmholtz resonator makes the sound pressure increase. In some cases, it is necessary to reduce the effective sound pressure. In this study, acoustic material is inserted to Helmholtz resonator for damping, and the resonator is applied to a sound tube for a basic study. As a result, the SPL is reduced using acoustic material. However, it is considered that the optimal reduction effect has not been obtained and it is necessary to change the resonant frequency of Helmholtz resonator. Next, the optimal value of the resonant frequency and the damping ratio of Helmholtz resonator is found, using identification of modal parameters and the theoretical formula of dynamic absorber's FRF.

A case-study on the continuous use of an in-ear dosimetric device

In order to further understand the combined effects of occupational and recreational noise exposure with regards to noise induced hearing loss (NIHL), an in-ear dosimeter prototype meant for continuous use was developed. The device acts as a hearing protection device (HPD) and can measure and log effective in-ear sound pressure level as well as unprotected levels. To enable its continuous use, this HPD is also equipped with a bypass feature for “transparent” hearing, input for music or communication devices and interfaces with Android smartphones. The proposed device allows for the implementation of an algorithm accounting for the auditory fatigue recovery rate, providing a true representation of the current accumulated noise dose. This allows for 24 h dosimetry and avoids having the user manually reset the dose back to 0% on the next day and thus assuming complete fatigue recovery has occurred. This paper details the proposed recovery algorithm, presents collected field data, and discusses the benefits as well as real-world challenges of using such a device.

Effective attenuation performance of passive hearing protectors: A temporary threshold shift study

Passive hearing protectors have been used for decades to reduce the risk of noise induced hearing loss. Hearing protectors (earmuffs, earplugs, helmets) have traditionally been the first line of defense for personnel working in hazardous noise environments. According to ANSI S12.68-2007, the “gold standard” method of estimating effective A-weighted sound pressure levels when hearing protectors are worn is the classical octave band method. The octave band method subtracts the hearing protector noise attenuation from the ambient noise level for each relevant octave band to estimate the noise exposure at the ear, under the hearing protector. ANSI S12.6-2008 Methods for Measuring the Real-Ear Attenuation of Hearing Protectors was used to measure the attenuation of the hearing protectors. The purpose of this study was to measure the effective attenuation of a hearing protector in terms of temporary threshold shift (TTS) response for individual human subjects with and without hearing protection. This presentation will include the TTS response curves for subjects exposed to various noise levels and durations in a controlled laboratory environment. The passive hearing protectors evaluated in this study included an earplug, earmuff, and a headphone with minimal attenuation as determined by REAT.

Attenuation performance of active noise reduction headsets using American National Standard s12.42 and the proposed U.S. Environmental Protection Agency Hearing Protector Labeling Regulation

The attenuation performance and noise reduction rating (NRR) of six commercially available active noise reduction (ANR) headsets was assessed using the proposed environmental protection agency (EPA) regulation. The passive attenuation results were collected using American National Standard Institute (ANSI) S12.6 method for measuring real-ear attenuation at threshold (REAT) of hearing protectors while the active attenuations results were collected using ANSI S12.42 methods for the measurement of insertion loss of hearing protection devices in continuous or impulsive noise using microphone-in-real-ear (MIRE) or acoustic test fixture procedures. ANSI/ASA S12.68 methods of estimating effective A-weighted sound pressure levels when hearing protectors are worn was used to compute noise reduction metrics including the noise reduction statistic A-weighted (NRSA) and the graphical noise reduction statistic (NRSG). The proposed NRR labels for the ANR headsets were computer per the guidance in the draft U.S. EPA regulation. The presentation will include the baseline passive, active, and total attenuation, the NRSA and the Graphical NRSG, and the proposed EPA labels for passive attenuation and total attenuation while in an active mode.

Quantitative measurement of pass-by noise radiated by vehicles running at high speeds

It has been a challenge in the past to accurately locate and quantify the pass-by noise source radiated by the running vehicles. A system composed of a microphone array is developed in our current work to do this work. An acoustic-holography method for moving sound sources is designed to handle the Doppler effect effectively in the time domain. The effective sound pressure distribution is reconstructed on the surface of a running vehicle. The method has achieved a high calculation efficiency and is able to quantitatively measure the sound pressure at the sound source and identify the location of the main sound source. The method is also validated by the simulation experiments and the measurement tests with known moving speakers. Finally, the engine noise, tire noise, exhaust noise and wind noise of the vehicle running at different speeds are successfully identified by this method.

Attenuation performance of double hearing protection devices.

High performance jet aircraft are capable of producing 130-150 dB of noise. Large populations work long hours in these high level noise environments and are at risk of hearing loss and related hearing disabilities. An array of hearing protection devices (HPD), both single hearing protection (SHP) and double hearing protection (DHP), are issued to protect aircrew and ground crew members from the nearly constant assault of hazardous noise. American National Standard Institute (ANSI) Methods for Measuring the Real-Ear Attenuation (REAT) of Hearing Protectors S12.6 were used to measure attenuation performance of nearly 20 SHP and DHP configurations. The term DHP can be slightly deceiving. DHP means two devices are worn in combination, not the sum of the attenuation from each device worn singly. The passive attenuation performance of inserts (earplugs) and helmets worn singly and in combination were reported using REAT octave band data, EPA Noise Reduction Ratings (NRR), and ANSI Methods of Estimating Effective A-Weighted Sound Pressure Levels when Hearing Protectors are Worn: the Noise Level Reduction Statistics for use with A-Weighting (NRSA), and the Noise Level Reduction Statistic, Graphical (NRSG).

Near-field acoustics of clustered rocket engines

This paper presents an approach for the prediction and characterization of the near-field acoustic levels from closely spaced clustered rocket engines. The calculations are based on the method proposed by Eldred wherein the flow field from the clustered rockets is divided into two zones. Zone 1 contains the isolated nozzles that produce noise independently and extends up to a distance where the individual flows completely mix to form an equivalent single nozzle flow. Zone 2 is occupied by the single mixed stream starting from the station where the jets merge. The acoustic fields from the two zones are computed separately on the basis of the NASA-SP method developed for a single equivalent nozzle. A summation of the spectra for the two zones yields the total effective sound pressure level for the clustered engines. Under certain conditions of nozzle spacing and flow parameters, the combined sound pressure level spectrum for the clustered nozzles displays a double peak. Test cases are presented here to demonstrate the importance of hydrodynamic interactions responsible for the double peak in the sound spectrum in the case of clustered rocket nozzles, and the role of ground reflections in the case of noninterfering jets.

118 音響励起による翼型の空力特性の改善(騒音・振動対策の最前線(2),騒音・振動評価・改善技術)

Acoustic excitation was used for method to prompt reattachment on airfoils. However several studies have been made on acoustic excitation, little attention has been given to the reattachment process in terms of turbulent intensity in separation shear layer. Then we will discuss the effect of sound on separation shear layer in this paper. According to the performance test and velocity measurement in boundary layer, we confirmed that the lift coefficient increase and drag coefficient decrease by acoustic excitation. We can interpret this phenomenon in the following way: Firstly, the separation boundary layer is disturbed by radiating the sound. This sound of frequency equals to the period of flow fluctuation in separation boundary layer. Secondly, turbulent intensity increased near the reattachment point. Finally, Reattachment is prompted. Additionally, we recognized that the effective frequency is 160Hz〜180Hz, effective sound pressure level is approximately 63dB for MEL12m84.

Impact of seismic surveys on marine life

The possible impact of marine seismic surveys on marine life has been of great concern for many years. The discussion is, however, characterized by confusion over sound-level terms and measurements, as well as an apparent misunderstanding of the nature of seismic signals. This paper will review underwater sound and the nature of impulse sound as it may impact marine life in general. A seismic signal is quantified by a variety of measures in the time and frequency domains. Factors such as peak pressure and the rate of pressure change have impact on the quality of the seismic data. But they will also be of importance for the evaluation of possible impact that the signals may have on marine life. Pressure output from the source is measured in Newton/m2 or Pascal (Pa) but is most often given on a decibel scale. Intensity and effective sound pressure (Pe) are related through the equation \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[I = \frac{P\_{e}^{2}}{{\rho}\_{0}c}\] \end{document} where I is the specific density and c is the propagation speed of sound. This gives the basis for the decibel scale for sound intensity or pressure as \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[dB = 10log\frac{I\_{1}}{I\_{0}} = 20log \frac{P}{P_{0}}\] \end{document} where I is the reference intensity level (watts/m2) and P is the reference pressure in Newton/m2 (Pascal) ρ c is often referred to as the acoustic impedance of the medium. A value of 415 is used for air and 1.54 × 106 is the standard value for seawater. Sound intensity, or pressure, will cause an amplitude displacement of molecules that is given by \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[A = \frac{1}{{\omega}}\sqrt{\frac{I}{{\rho}\_{0}c}} = \frac{P}{{\omega}{\rho}\_{0}c}\] \end{document} The lower limit of hearing for the human ear corresponds to a pressure level of 20.4 μPa. This value is used as the reference pressure for acoustic measurements in air. In water the reference pressure is 1 μPa. The difference between these reference pressures is 26 dB. In water, due to …

Investigation of heat transfer from circular cylinders in high power 10 kHz and 20 kHz acoustic resonant fields

This paper reports on the experimental results of heat transfer in 10 and 20 kHz acoustic resonant standing wave fields for a small cylinder by means of hot-film anemometry. To obtain the high power 10 and 20 kHz acoustic resonant standing wave fields, pairs of oscillating transmitters, each working with slightly different frequencies, were employed. It is shown that the effective sound pressure depends on several parameters like the irradiation number, the amplitude of the transmitters, the impedance, and the frequency. An empirical equation is given to calculate the effective sound pressure in the acoustic standing wave field. A remarkable enhancement of the heat transfer can be observed in the acoustic field compared to free convection. Finally, a correlation is given to predict the heat transfer in such acoustic fields. This correlation is valid for a wide range of Reynolds numbers (4–3 000).

Test chamber for determining damage thresholds for high-amplitude underwater sound exposure in animal models

In order to determine the effects of low-frequency underwater sound on small animal models it is desirable to expose them to well-characterized fields which closely simulate the (locally) plane-wave open ocean stimulus. It is also desirable to produce pure pressure and acceleration stimuli to isolate the effects of the individual components of the acoustic plane wave. It is necessary to produce sufficiently strong signals to enable damage thresholds to be determined. The range of frequencies over which such stimuli must be produced is quite broad since it must include the actual band of interest (100–500 Hz) to examine damage on a cellular and tissue level, as well as at scaled frequencies (∼1–5 kHz) to examine the effects of organ structure. The problem is subtler than one might imagine because of the high compliance of the test animals due to the air in their lungs. The lungs will drastically alter the acoustic field in the chamber and change the loading on the sources and the chamber could alter the vibrational response of the lung. Careful consideration is required to ascertain what is required of the chamber to assure valid measurements and to determine the true effective sound pressure level.

乳突洞口閉鎖効果 ツチ骨変位振幅測定法と鼓膜内外音圧差測定法による検討

Effect of attic obstruction on the middle ear sound transmission was measured simultaneously by two different methods in four fresh human cadaver temporal bones. In the visual method, the displacement of the manubrium tip of the malleus (umbo) to a constant sound pressure of 124dB SPL at the TM was measured before and after attic obstruction under microscope with stroboscope illumination combined with a video measuring system. In the acoustical method, the effective sound pressure (SP) which was transformed into the energy of vibration of the TM, was measured before and after obstruction of the attic. The effective SP was obtained from three parameters; the SPs in front and behind the TM, and the phase difference between them. The results by two methods were in good accordance and showed that the attic obstruction improved middle ear sound transmission by 7±2dB at 2.4-3kHz and worsened it by 6±2dB at 0.6-0.8kHz.

ＴＩＧ溶接アーク音特性におよぼす電流波形の影響―溶接アーク音に関する研究 ＩＩＩ

Investigations have been made of the effects of the rectangle, sawtooth, triangle and sine current waveforms on the welding arc sound of TIG arc, that is a stationary arc on the water cooled copper plate, by means of a transistor control type power source.The experimental results have indicated that the welding arc sound depends on the current wavetorm, repetition frequency fp and amplitude τp. The welding arc sound is composed of a fundamental tone which has a frequency spectrum of fp and its harmonics. An excellent frequency spectrum fig agrees with fp in the triangle and sine wave current, but fox changes to higher harmonic in the rectangle and sawtooth wave current.The effective sound pressure Pe is shown as a function of fp and τp(Pefpm⋅τpn), and the useful equations which are possible to estimate the noise level have been obtained.

Noise of deflectors used for flow attachment with STOL-OTW configurations

For future STOL aircraft utilizing engine-over-the-wing (OTW) installations in which the exhaust nozzles are located above and separated from the upper surface of the wing, an external jet-flow deflector can be used to provide flow attachment to the wing/flap surfaces for lift augmentation. In the present work, the deflector noise in the flyover plane measured with several model-scale nozzle/deflector configurations is examined. The OTW configurations consisted of a circular nozzle (5.18-cm diameter) mounted 0.1 wing chord lengths above and aft of the wing leading edge. Wing chords (flaps retracted) of 33 and 49.5 cm were used. Tests included flap settings of 20° and 60° and jet Mach numbers of 0.6 and 0.8. The data indicate that the effective sound pressure level of the deflector peaks in the forward quadrant. With some deflector/wing combinations, a severe tone/haystack was obtained at a model-scale frequency near 6-8000 Hz. The effective sound pressure level is a primary function of deflector immersion in the jet flow and the deflector span. Peak deflector noise levels as much as 12 dB above those of other jet/flap interaction noise sources were obtained.

Middle ear transmission in cats with experimentally induced tympanic membrane perforations.

A small perforation (2 mm2) was placed in the posterosuperior quadrant of the feline tympanic membrane (TM). Sound pressures (amplitudes and phases) required for a 10-μV round window cochlear microphonic (CM) output were measured at third-octave intervals from 200 to 4000 Hz (a) in front and behind the TM, (b) in open and closed sound systems, and (c) before and after perforation, as were the corresponding voltages across the transducer. Sound pressure (SP) changes in front of the TM after perforation revealed low-frequency losses, identical in shape and magnitude for both open and closed sound systems, that vary inversely with frequency at a rate of 12 dB/octave below 1600 Hz. The transducer voltage changes, concomitant with SP’s in front of the TM necessary to produce the criterion CM, paralleled the SP changes only in the open system. However, considerably larger voltage changes were found in the closed system, especially between 630 and 2000 Hz. Furthermore, from the SP’s measured on both sides of the TM, the mean effective sound pressure (SPeff) acting on the TM was calculated. The changes in SPeff, taken in reference to a constant CM output, demonstrate that a small TM perforation produces a 10-dB frequency-independent loss in transmission.

Acoustic signalling and its possible relationship to assembling and navigation in the moth, Heliothis zea

Evidence for the use of sensory modes other than olfaction in the assembly of moths is discussed. It is proposed that a multitude of sensing and signalling methods may be used. To support this hypothesis the rôle of ultrasonic emissions in Heliothis zea from the standpoint of its usefulness to the animal in communication and navigation was investigated. It was found that H. zea emits a rapidly damped 50 kc ultrasonic burst every 25 msec in synchronization with the wing beat, but not automatically produced by the wing beat. The burst is composed of two 185 μsec pulses of six oscillations each and the pulses are separated from each other by 190 μsec. Ultrasonic emissions were sporadic during the morning and afternoon hours, but became very regular in the late afternoon and evening. The effective sound pressure was greatest in the topside direction and least below. At a distance of 1·5 cm the average effective sound pressure was 98·5 dB re 0·0002 μbar. Using 0·02 μbar as the threshold for hearing in the moth, an analysis of the moth's acoustic capabilities was made. It was concluded that the ultrasonic emissions combined with the acoustic properties of the ears provided an echo-locating capability which could be used for the detection of large objects at a distance of over 2 m and the resolution of details down to 7 mm at distances up to 24 cm. Signalling for the purpose of assembling would be effective at distances of over 4 m and combined with olfactory information it should be of value in locating a mate.

Loudness, Sound Pressure, and Subglottal Pressure in Speech

Three experiments using one speaker and 30 listeners provided correlated data on subglottal pressure, average volume velocity through the glottis, fundamental frequency, effective sound pressure in front of the speaker, and judgments of loudness. Experiment 1: In 12 repetitions each of bee, bay, bar, bore, and boo spoken at various loudnesses, it was found that in the middle range (subglottal pressure) ∝ (effective sound pressure)0.6; and the level of the vowel in bar was about 5 dB greater than in bee or boo produced with the same subglottal pressure. Experiment 2: In 32 repetitions of the vowel /ɑ/ uttered at various loudnesses with the pitch uncontrolled, it was found that an increase of subglottal pressure of about 6.5 cm aq accompanied an increase in frequency of half an octave; and to a first approximation (rate of flow) ∝ (subglottal pressure). It follows that (rate of work done on the air) ∝ (subglottal pressure)2 ∝ (effective sound pressure)1.2. The exponent 1.2 compares well with the exponent 1.1 found by Lane, Catania, and Stevens for the autophonic response. Experiment 3: Thirty subjects judged the loudness of each word taken from Experiment 1 relative to the reference token in the frame Compare the words: bar and …. It was found that for any one vowel in the middle range, (loudness) ∝ (effective sound pressure)1.2, suggesting that subjects assessed the work done and not the auditory sensation in the usual way as found by Lane, Catania, and Stevens.

Measuring the Free Field Correction for a New Condenser Microphone

In the development of the new Bruel & Kjaer Measurement Condenser Microphone, it was found necessary to thoroughly investigate the diffraction characteristics and to use several calibration techniques to establish the difference between the microphone's free field and pressure response. The techniques and results of these investigations are described as the following: (A) Measuring the pressure distribution around a model of the microphone placed in a free sound field and the sensitivity distribution over the microphone diaphram. In conjunction with measurements made with a specially designed concentric electrostatic actuator, the effective sound pressure increase on the diaphram is calculated. (B) Measuring the microphone sensitivity as a function of frequency according to the free-field reciprocity method, and comparing the results with the pressure response of the same microphones measured by means of the electrostatic actuator method. The free-field correction obtained by the two different methods (A) and (B) showed excellent agreement.