scholarly journals Spatial reconstruction of the sound field in a room in the modal frequency range using Bayesian inference

2021 ◽  
Vol 150 (6) ◽  
pp. 4385-4394
Author(s):  
Jonas M. Schmid ◽  
Efren Fernandez-Grande ◽  
Manuel Hahmann ◽  
Caglar Gurbuz ◽  
Martin Eser ◽  
...  
Keyword(s):  
Bayesian Inference ◽  
Sound Field ◽  
Frequency Range ◽  
Modal Frequency ◽  
Spatial Reconstruction

Study on acoustic and flow-induced noise characteristics of L-shaped duct with a shallow cavity

2020 ◽  
Vol 68 (3) ◽  
pp. 209-225
Author(s):  
Masaaki Mori ◽  
Kunihiko Ishihara
Keyword(s):  
Air Conditioning ◽  
Sound Field ◽  
Frequency Range ◽  
Acoustic Characteristics ◽  
Inflow Velocity ◽  
Aerodynamic Sound ◽  
Noise Characteristics ◽  
Flow Induced Noise ◽  
Shallow Cavity ◽  
Conditioning Equipment

An aerodynamic sound generated by a flow inside a duct is one of the noise pro- blems. Flows in ducts with uneven surfaces such as grooves or cavities can be seen in various industrial devices and industrial products such as air-conditioning equipment in various plants or piping products. In this article, we have performed experiments and simulations to clarify acoustic and flow-induced sound characteris- tics of L-shaped duct with a shallow cavity installed. The experiments and simula- tions were performed under several inflow velocity conditions. The results show that the characteristics of the flow-induced sound in the duct are strongly affected by the acoustic characteristics of the duct interior sound field and the location of the shallow cavity. Especially, it was found that the acoustic characteristics were af- fected by the location of the shallow cavity in the frequency range between 1000 Hz and 1700 Hz.

scholarly journals THE PECULIARITIES OF THE SOUND FIELD ENERGY DECAY IN A ROOM WITH THE USE OF DIFFERENT PULSED SOUND SOURCES/GARSO LAUKO ENERGIJOS SLOPIMO PATALPOJE YPATUMAI, NAUDOJANT SKIRTINGUS IMPULSINIUS GARSO ŠALTINIUS

1999 ◽  
Vol 5 (2) ◽  
pp. 135-140
Author(s):  
Vytautas Stauskis
Keyword(s):  
Noise Level ◽  
Sound Field ◽  
Maximum Energy ◽  
Reverberation Time ◽  
Frequency Range ◽  
Sound Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Difference ◽  
Field Decay

The paper deals with the differences between the energy created by four different pulsed sound sources, ie a sound gun, a start gun, a toy gun, and a hunting gun. A knowledge of the differences between the maximum energy and the minimum energy, or the signal-noise ratio, is necessary to correctly calculate the frequency dependence of reverberation time. It has been established by investigations that the maximum energy excited by the sound gun is within the frequency range of 250 to 2000 Hz. It decreases by about 28 dB at the low frequencies. The character of change in the energy created by the hunting gun differs from that of the sound gun. There is no change in the maximum energy within the frequency range of 63–100 Hz, whereas afterwards it increases with the increase in frequency but only to the limit of 2000 Hz. In the frequency range of 63–500 Hz, the energy excited by the hunting gun is lower by 15–30 dB than that of the sound gun. As frequency increases the difference is reduced and amounts to 5–10 dB. The maximum energy of the start gun is lower by 4–5 dB than that of the hunting gun in the frequency range of up to 1000 Hz, while afterwards the difference is insignificant. In the frequency range of 125–250 Hz, the maximum energy generated by the sound gun exceeds that generated by the hunting gun by 20 dB, that by the start gun by 25 dB, and that by the toy gun—by as much as 35 dB. The maximum energy emitted by it occupies a wide frequency range of 250 to 2000 Hz. Thus, the sound gun has an advantage over the other three sound sources from the point of view of maximum energy. Up until 500 Hz the character of change in the direct sound energy is similar for all types of sources. The maximum energy of direct sound is also created by the sound gun and it increases along with frequency, the maximum values being reached at 500 Hz and 1000 Hz. The maximum energy of the hunting gun in the frequency range of 125—500 Hz is lower by about 20 dB than that of the sound gun, while the maximum energy of the toy gun is lower by about 25 dB. The maximum of the direct sound energy generated by the hunting gun, the start gun and the toy gun is found at high frequencies, ie at 1000 Hz and 2000 Hz, while the sound gun generates the maximum energy at 500 Hz and 1000 Hz. Thus, the best results are obtained when the energy is emitted by the sound gun. When the sound field is generated by the sound gun, the difference between the maximum energy and the noise level is about 35 dB at 63 Hz, while the use of the hunting gun reduces the difference to about 20–22 dB. The start gun emits only small quantities of low frequencies and is not suitable for room's acoustical analysis at 63 Hz. At the frequency of 80 Hz, the difference between the maximum energy and the noise level makes up about 50 dB, when the sound field is generated by the sound gun, and about 27 dB, when it is generated by the hunting gun. When the start gun is used, the difference between the maximum signal and the noise level is as small as 20 dB, which is not sufficient to make a reverberation time analysis correctly. At the frequency of 100 Hz, the difference of about 55 dB between the maximum energy and the noise level is only achieved by the sound gun. The hunting gun, the start gun and the toy gun create the decrease of about 25 dB, which is not sufficient for the calculation of the reverberation time. At the frequency of 125 Hz, a sufficiently large difference in the sound field decay amounting to about 40 dB is created by the sound gun, the hunting gun and the start gun, though the character of the sound field curve decay of the latter is different from the former two. At 250 Hz, the sound gun produces a field decay difference of almost 60 dB, the hunting gun almost 50 dB, the start gun almost 40 dB, and the toy gun about 45 dB. At 500 Hz, the sound field decay is sufficient when any of the four sound sources is used. The energy difference created by the sound gun is as large as 70 dB, by the hunting gun 50 dB, by the start gun 52 dB, and by the toy gun 48 dB. Such energy differences are sufficient for the analysis of acoustic indicators. At the high frequencies of 1000 to 4000 Hz, all the four sound sources used, even the toy gun, produce a good difference of the sound field decay and in all cases it is possible to analyse the reverberation process at varied intervals of the sound level decay.

Characteristics of Modal Sound Radiation of Finite Cylindrical Shells

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Tian Ran Lin ◽  
Chris Mechefske ◽  
Peter O’Shea
Keyword(s):  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Radiation Efficiency ◽  
Boundary Element Methods ◽  
Frequency Range ◽  
Nodal Lines ◽  
Infinite Cylindrical Shell ◽  
Modal Index

Characteristics of modal sound radiation of finite cylindrical shells are studied using finite element and boundary element methods in this paper. In the low frequency range, modal radiation efficiencies of finite cylindrical shells are found to asymptotically approach those of the corresponding infinite cylindrical shell when structural trace wavelengths of the cylindrical shells are greater than the acoustic wavelength. Modal radiation efficiencies for each group of modes having the same circumferential modal index decrease as the axial modal index increases. They converge to each other when the axial trace wavelength is much greater than the circumferential trace wavelength. The mechanism leading to lower radiation efficiency of modes with higher circumferential modal index of short cylinders is explained. Similar to those of flat plate panels, change in slope or waviness is observed in modal radiation efficiency curves of modes with higher order axial modal index at medium frequencies. This is attributed to the interference of sound radiated by neighboring vibrating cells when the distance between nodal lines of a vibrating mode is in the same order or smaller than the acoustic wavelength. The effects of the internal sound field on modal radiation efficiencies of a finite open-end cylinder are discussed.

Active Control of Low-Frequency Sound Radiation From Vibrating Panel Using Planar Sound Sources

2001 ◽  
Vol 124 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Kean Chen ◽  
Gary H. Koopmann
Keyword(s):  
Active Control ◽  
Near Field ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Field ◽  
Sound Power ◽  
Frequency Range ◽  
Sound Sources ◽  
Frequency Sound ◽  
Secondary Sources

Active control of low frequency sound radiation using planar secondary sources is theoretically investigated in this paper. The primary sound field originates from a vibrating panel and the planar sources are modeled as simply supported rectangular panels in an infinite baffle. The sound power of the primary and secondary panels are calculated using a near field approach, and then a series of formulas are derived to obtain the optimum reduction in sound power based on minimization of the total radiate sound power. Finally, active reduction for a number of secondary panel arrangements is examined and it is concluded that when the modal distribution of the secondary panel does not coincide with that of the primary panel, one secondary panel is sufficient. Otherwise four secondary panels can guarantee considerable reduction in sound power over entire frequency range of interest.

scholarly journals IDENTIFICATION OF NORMAL WAVES FORMING A SOUND FIELD IN A SHALLOW SEA AT THE INFRASONIC FREQUENCY RANGE. Part II

2020 ◽  
Author(s):  
С.Б. Касаткин
Keyword(s):  
Experimental Studies ◽  
Sound Field ◽  
Noise Signal ◽  
Energy Structure ◽  
Frequency Range ◽  
Field Zone ◽  
Normal Waves ◽  
Infrasonic Frequency ◽  
Scholte Waves ◽  
Scholte Wave

Анализируются результаты экспериментальных исследований звукового поля, зарегистрированного комбинированными приемниками, образующими вертикально ориентированную двухэлементную антенну. Звуковое поле формировалось дискретными составляющими вально-лопастного звукоряда шумового сигнала НИС «Юрий Молоков» в инфразвуковом диапазоне частот 2–20 Гц, а также буксируемым низкочастотным излучателем полигармонического сигнала в диапазоне частот 30–60 Гц. Глубина моря и рабочий диапазон частот 2–20 Гц исключали возможность возбуждения нормальных волн дискретного спектра в модельном волноводе Пекериса в этом диапазоне частот. По результатам спектрального анализа шумового сигнала получена оценка потенциальной помехоустойчивости комбинированного приемника при использовании полного набора информативных параметров, характеризующих энергетическую структуру звукового поля. По результатам анализа вертикальной структуры звукового поля в инфразвуковом диапазоне частот был сделан вывод о том, что звуковое поле сформировано неоднородными нормальными волнами Шолте, регулярной и обобщенной (гибридной). В дальней зоне источника доминирует регулярная волна Шолте, локализованная на границы раздела вода – морское дно. В ближней зоне источника возрастает роль обобщенной волны Шолте, локализованной на горизонте источника, а звуковое поле формируется парой волн Шолте, регулярной и обобщенной. The results of experimental studies of the sound field recorded by combined receivers forming a vertically oriented two-element antenna are analyzed. The sound field was formed by discrete components of the vane-blade scale of the noise signal of the science ship «Yuri Molokov» in the infrasonic frequency range of 2–20 Hz, as well as by a towed low-frequency emitter of a polyharmonic signal in the frequency range 30–60 Hz. The depth of the sea and the operating frequency range of 2–20 Hz excluded the possibility of exciting normal waves of the discrete spectrum in the model Pekeris waveguide in this frequency range. Based on the results of spectral analysis of the noise signal, an estimate of the potential noise immunity of the combined receiver was obtained using a full set of informative parameters characterizing the energy structure of the sound field. Based on the results of the analysis of the vertical structure of the sound field in the infrasonic frequency range, it was concluded that the sound field is formed by inhomogeneous normal Scholte waves, regular and generalized (hybrid). In the far zone of the source, a regular Scholte wave dominates, localized at the water – seabed interface. In the near-field zone of the source, the role of the generalized Scholte wave localized at the source horizon increases, and the sound field is formed by a pair of Scholte waves, regular and generalized.

Results of tests on the indicator of external noise of electric locomotives in the standing time

2017 ◽  
Vol 76 (5) ◽  
pp. 301-305 ◽  
Author(s):  
M. Yu. Noskov ◽  
M. M. Ginshparg ◽  
N. S. Nesterov
Keyword(s):  
Spectral Composition ◽  
Sound Field ◽  
Alternating Current ◽  
External Noise ◽  
Stationary Mode ◽  
Frequency Range ◽  
Electric Locomotive ◽  
Standing Time ◽  
Test Loop ◽  
Absorbing Material

The authors of the Test Loop of the JSC “VNIIZhT” had conducted tests of mainline electric locomotives intended for handling freight trains on sections of the road electrified with alternating current at a voltage of 25 kV (electric locomotives of an alternating current). Tests were conducted in terms of the level of external noise at the standing time. The results of tests of AC electric locomotive, which was in a stationary mode, are presented in terms of the external noise index, and a methodology for performing these tests is described. As a result of the conducted researches, the article establish the main sources of external noise in the operation of AC electric locomotives (fans intended for cooling electrical equipment and traction motors, air compressors, traction transformers, etc.), its actual values, as well as the nature of the sound field around electric locomotives. The analysis of the obtained sound field made it possible to identify the points where the excess of the standard noise values (more than 65 dBA) is observed. It is proposed to bring the technical condition of the equipment, such as traction transformer, converter and cooling module of the traction engine of the power compartment of an electric locomotive in accordance with the normative documentation. The repeated measurements of the external noise level after technical completion did not reveal the excess of its normative values in accordance with the regulatory documentation. In order to provide a normative margin in terms of the external noise of an electric locomotive, it is proposed to use sound-absorbing material in the construction of its body. It is recommended to perform an experimental study of the spectral composition of the noise of the equipment of an electric locomotive operating at the standing time and the resulting external noise at points located outside and around the locomotive in order to calculate the acoustic characteristics of sound-absorbing materials. Sound absorbing material is expedient to be selected depending on the frequency range in which the greatest excess is observed above the maximum permissible values using known empirical and semi-empirical dependences, on the basis of which it is possible to preliminary determine its sound-absorbing properties in the frequency range established by regulatory documents. After equipping the power compartment of the locomotive with soundproof materials, tests on the evaluation of the external noise of an electric locomotive at standing should be repeated.

scholarly journals An investigation of the performance of the Rayleigh disk

1945 ◽  
Vol 183 (994) ◽  
pp. 296-316 ◽  
Keyword(s):  
Finite Thickness ◽  
Sound Field ◽  
Particle Method ◽  
Reference Standard ◽  
Audio Frequency ◽  
Frequency Range ◽  
Smoke Particle ◽  
Oscillatory Velocity ◽  
Continued Use ◽  
The Stability

The paper describes an investigation of the nature of the law which governs the torque on a Rayleigh disk suspended in a sound field. The torque is found to follow an expression of the form obtained theoretically by König, provided that factors such as the finite thickness of the disk and the lack of infinite inertia of the disk are taken into account. The measurements were made at frequencies spread over the range 250-4000 cyc./sec. The correction to the torque in König’s formula made necessary by the thickness of the disk is shown to be large and to have a sign opposite to that determined theoretically by König for ellipsoidal disks. The influence upon the torque of the proximity of the wall of a tube has been investigated. The nature of the precautions which should be observed in choosing the form of a Rayleigh disk are discussed with reference to reducing to a minimum the effects on the torque of the thickness and mobility of the disk and of diffraction of sound by the disk. An investigation has been made of the numerical factor which relates the magnitudes of the torque to the other variables of König’s formula. This part of the investigation reduces essentially to the measurement of the oscillatory velocity of the field in which the disk is situated. The smoke-particle method of Andrade and of Carrière was adapted for the above purpose, and it was found possible to make determinations of oscillatory velocity within about 1 % for frequencies up to 4000 cyc./sec. Measurements have been made of the torque on a Rayleigh disk of known dimensions in terms of the oscillatory velocity for frequencies in the range 250-4000 cyc./sec. Discrepancies of 3·5 % in velocity (7 % in torque) are shown to follow from the use of König’s formula, and these results confirm, and extend into the audio-frequency range, the investigations of Herrington & Oatley in the band 9-22 cyc./sec. The experimental work confirms that the stability of behaviour of the Rayleigh disk justifies its continued use as a reference standard of acoustical intensity but shows that in setting up the reference standard, corrections amounting in extreme cases to 0·3 db. must be applied to the intensity as determined from König’s formula.

An Introduction to Virtual Phased Arrays for Beamforming Applications

2015 ◽  
Vol 39 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Daniel Fernández Comesana ◽  
Keith R. Holland ◽  
Dolores García Escribano ◽  
Hans-Elias de Bree
Keyword(s):  
Sound Localization ◽  
Relative Phase ◽  
Phased Arrays ◽  
Sound Field ◽  
Microphone Arrays ◽  
Acoustic Sensor ◽  
Frequency Range ◽  
Acoustic Holography ◽  
Sound Sources ◽  
Single Sensor

Abstract Sound localization problems are usually tackled by the acquisition of data from phased microphone arrays and the application of acoustic holography or beamforming algorithms. However, the number of sensors required to achieve reliable results is often prohibitive, particularly if the frequency range of interest is wide. It is shown that the number of sensors required can be reduced dramatically providing the sound field is time stationary. The use of scanning techniques such as “Scan & Paint” allows for the gathering of data across a sound field in a fast and efficient way, using a single sensor and webcam only. It is also possible to characterize the relative phase field by including an additional static microphone during the acquisition process. This paper presents the theoretical and experimental basis of the proposed method to localise sound sources using only one fixed microphone and one moving acoustic sensor. The accuracy and resolution of the method have been proven to be comparable to large microphone arrays, thus constituting the so called “virtual phased arrays”.

scholarly journals SIMILARITY BETWEEN ACOUSTIC INDICATORS OF AN REAL HALL AND ITS MODEL/REALIOS SALĖS IR JOS MODELIO AKUSTINIŲ RODIKLIŲ PANAŠUMAS

1999 ◽  
Vol 5 (1) ◽  
pp. 68-73
Author(s):  
Vytautas Stauskis
Keyword(s):  
Sound Source ◽  
Sound Absorption ◽  
Sound Field ◽  
Computer Memory ◽  
Digital Converter ◽  
Reverberation Time ◽  
Frequency Range ◽  
Analog To Digital ◽  
The Real ◽  
The Difference

The similarity between acoustic indicators of an real hall and its model has been examined. A rectangular hall is 13.6 m long, 10.7 m wide and 7.0 m high. Its floor and ceiling are horizontal. The hall has plastered walls, parquet floor, and reinforced-concrete-slab ceiling. Thus, all surfaces of the hall are made of materials that reflect sound well. A hall model scaled 1:25 was made. The floor and ceiling of the model were made of fabric-based laminate and the walls were made of veneer 8 mm thick, lacquered three times. Therefore, the materials used to produce the model are similar to those of the real hall by their sound absorption properties. A 9 calibre sound pistol was used as a sound source for the investigations in the real hall. The sound signal was stored in the computer memory via a ½′ microphone, an amplifier and an analog-to-digital converter, then analysed by means of a acoustical signal analysis program developed by us. The signal was analysed within the frequency range of 50—5000 Hz. The main objective and subjective acoustical indicators of the hall were calculated using this program. A spark sound source was used for the experiments with the hall model. It was thrust through a hole in the floor in order to improve the radiation directivity diagram. The position of the sound source and a ¼′ microphone was the same in the real hall and its model. The signal was fed from the microphone to the amplifier, then to the analog-to-digital converter and recorded in the computer memory. The signal may be recorded via several different buffers allowing to record signals of varied length. The range of the frequencies investigated was from 1250 to 50000 Hz, the model scale being 1:25. The signal digitization frequency was 166.6 kHz and the digitization time was 6 mks. The decrease of the sound field of a non-filtered signal is of a similar nature during the first and the last 400 ms, i e during the early and the late periods of decrease. In the intermediate period, approximately from 500 to 3000 ms, the sound field decrease in the model exceeds the one in the real hall by only 1–3 dB. In the real hall, the sound field decrease is close to the straight line up to 2500 ms, while in the model—up to 1000 ms only, and the decrease is faster than in actual practice. The further field decrease has the character of a curve and the diffusive properties of the field are impaired. These results show that the sound field decrease in the real hall and in the model is quite similar. Investigations show that the sound field decrease in the real hall and in the model is almost analogous when the decrease is approximated every 10 dB from 0 to—30 dB. The reverberation time difference is 0.16–0.5 s and is lower than 10%. As the field decrease is approximated from − 5 to −35 dB, the reverberation time of the model exceeds that of the real hall by about 1 s, which makes up about 15%. The difference between the early reverberation time of the real hall and its model is only − 0.2 − 0.8 s even up to 500 Hz. This is mainly determined by the air sound absorption in the model at the ultrasound frequencies. As the sound field decrease is approximated from 0 to − 30 dB and from −5 to −35 dB, the difference between the reverberation time of the hall and its model in the frequency range up to 500 Hz is slight, only 0.2–0.9 s, which is less than 15%. The character of change in the sound absorption is analogous to that of the sound absorption coefficients. In the range up to 500 Hz, the sound absorption of the real hall and its model differs by 1–2 m2 only. As frequency increase, the difference reaches − 20 m2. For a non-filtered signal, the music sound clarity index C 80 is 5.6 dB for the real hall and 4.9 dB for the model.

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