scholarly journals A New Method for Sound Generation Based on Digital Sound Reconstruction

2021 ◽  
Vol 29 (04) ◽  
Author(s):  
Dominik Mayrhofer ◽  
Manfred Kaltenbacher
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
New Method ◽  
General Idea ◽  
Sound Generation ◽  
Frequency Range ◽  
Numerical Investigations ◽  
Multiple Array ◽  
Depth View ◽  
Digital Sound

In this paper, we consider the general idea of Digital Sound Reconstruction (DSR) and analyze its inherent limitations. Based on this discussion, a new method which we call Advanced Digital Sound Reconstruction (ADSR) is introduced and analyzed in detail. This method aims to overcome the problems of classical DSR by introducing shutter gates and focuses on sound generation in the low-frequency domain. Combining the idea of classical DSR with a redirection mechanism leads to a gain of 20[Formula: see text]dB per decade regarding the sound pressure for decreasing frequency values. We present multiple array designs and possible embodiments for ADSR as well as an in depth view of excitation and optimization approaches. Finally, numerical investigations are used in order to demonstrate the potential of ADSR especially in the mid- to low-frequency range.

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.

Reverberant Chamber Enhancement

2015 ◽  
Vol 58 (1) ◽  
pp. 24-36
Author(s):  
Daniel Hayes
Keyword(s):  
Fundamental Mode ◽  
Research Laboratory ◽  
Sound Pressure ◽  
Low Frequency ◽  
Naval Research ◽  
Frequency Range ◽  
Testing Frequency ◽  
Acoustic Testing ◽  
High Sound ◽  
High Pass

Typical reverberant chambers used for High Intensity Acoustic Testing (HIAT) can achieve high sound pressure levels (SPL) across most of the applicable frequency range (20 Hz to 10 kHz), but they have limitations. Depending on the size of the chamber, low frequency chamber modes may be limited in the testing frequency range. In addition, reverberant chambers that use conventional 1/3-Octave controllers are not able to control low frequency chamber modes as effectively as the higher frequencies. A typical response to this inability to control the chamber modes is to high pass the frequency range of the excitation in the chamber to prevent exciting the low frequency modes. This method protects the test article from over-testing, although it also might under-test an article that has a fundamental mode below the high-pass frequency of the chamber. Recently, Maryland Sound International conducted a test at the Naval Research Laboratory (NRL) to determine if Direct Field Acoustic Testing (DFAT) technology could be applied to conventional reverberant chambers.

Procedure for determination of sound power levels of direct-radiator loudspeakers in the low-frequency range using the sound pressure within the system enclosure

2015 ◽  
Vol 96 ◽  
pp. 75-82 ◽  
Author(s):  
José Luis Sánchez Bote ◽  
Juan Sancho Gil ◽  
Francisco Aznar Ballesta ◽  
Lino Pedro García Morales
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Sound Power ◽  
Frequency Range

scholarly journals Investigation of a new method for sound generation – Advanced Digital Sound Reconstruction

2021 ◽  
Author(s):  
Dominik Mayrhofer ◽  
Manfred Kaltenbacher
Keyword(s):  
Production Efficiency ◽  
Low Frequency ◽  
Micro Electro Mechanical System ◽  
General Description ◽  
Mems Devices ◽  
Sound Generation ◽  
Audio Signals ◽  
Excitation Scheme ◽  
Mems Technology ◽  
Digital Sound

AbstractThe current loudspeaker market has a high demand for portable audio devices. Hence, the miniaturization of loudspeakers (microspeakers) is of great importance for manufacturers. Traditional loudspeakers – for example the electrodynamic loudspeaker – are the forerunners, but so-called MEMS loudspeakers (Micro-Electro-Mechanical-System) have emerged recently. MEMS devices have already been used for sensors (i.e., microphones) to a great extend due to their advantages regarding form factor and production efficiency. Albeit additional challenges for actuators like moving enough air with a microstructure – as it is the case for a loudspeaker – the usage of MEMS technology for loudspeakers is very attractive.Since especially low-frequency audio signals often pose problems for microspeakers, this article focuses on a new sound generation technique called Advanced Digital Sound Reconstruction (ADSR) which is especially well-suited for low-frequency audio signals since ADSR can generate more volume displacement relative to its size. Based on a general description of the principle, an outlook of the possibilities regarding achievable sound pressure compared to the classical excitation scheme is derived. Furthermore, measurements are presented, which aim to prove the concept of ADSR based on already existing actuators.

scholarly journals The Sound of Gas-Turbine Installations

1970 ◽  
Author(s):  
Robert M. Hoover
Keyword(s):  
Control Problem ◽  
Gas Turbine ◽  
Sound Pressure ◽  
Noise Control ◽  
Low Frequency ◽  
Frequency Range ◽  
Level Data ◽  
Industry Performance ◽  
Noise Measurements ◽  
Control Criteria

In this overall review of gas-turbine sound and its control, the author discusses the variety of installations, the scope of the noise control problem, criteria, industry performance, noise specifications, and noise measurements. In particular, the magnitude of the noise control problem is indicated by discussion of the sound of an unmuffled 20 Mw turbine. Typical sound pressure level data on current installations are given, and suggestions are made for noise control criteria in the low frequency range.

scholarly journals A New Method for Non-Invasive Measurement of Skin in the Low Frequency Range

2010 ◽  
Vol 16 (3) ◽  
pp. 143 ◽  
Author(s):  
Min Soo Kim ◽  
Youngchang Cho ◽  
Suk-Tae Seo ◽  
Chang-Sik Son ◽  
Hee-Joon Park ◽  
...  
Keyword(s):  
Low Frequency ◽  
New Method ◽  
Frequency Range ◽  
Non Invasive ◽  
Invasive Measurement

scholarly journals DEVELOPMENT OF SMALL-SIZE LOW-FREQUENCY PRESSURE GRADIENT SENSORS

2020 ◽  
Author(s):  
В.И. Коренбаум ◽  
С.В. Горовой ◽  
А.А. Тагильцев ◽  
А.Е. Бородин
Keyword(s):  
Pressure Gradient ◽  
Sound Pressure ◽  
Dynamic Range ◽  
Linear Array ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Differential Pressure ◽  
Effective Pressure ◽  
Frequency Range

Проанализированы проблемы создания приемников градиента давления различных типов для использования в низкочастотном диапазоне, определяемые необходимостью достижения достаточной чувствительности к звуковому давлению в плоской волне, коэффициента деления дипольной характеристики направленности не хуже 26 дБ, динамического диапазона не менее 80–100 дБ. Теоретически оценены пределы применимости ПГД 2-гидрофонного (разностного) типов по волновым размерам. Разработаны высоко- эффективные ПГД инерционного и силового типов. Предложено комбинирование ПГД инерционного/силового и 2-гидрофонного типов в линейной антенне. The problems of development of pressure gradient sensors of various types for usage in low-frequency range are analyzed, which are connected to a necessity to provide acceptable sensitivity to sound pressure in a flat wave, minima of the dipole directivity pattern being nor less 26 dB, dynamic range being nor less 80–100 dB. The wavelength limits of acceptability of 2-hydrophone (differential) pressure gradient sensors are theoretically predicted. High effective pressure gradient sensors of inertial and force types are designed. It is suggested to combine a pressure gradient sensor of inertial or force type with the pressure gradient sensor of 2-hydrophone type in linear array.

scholarly journals Improved Source Characteristics of a Handclap for Acoustic Measurements: Utilization of a Leather Glove

Acoustics ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 803-811
Author(s):  
Rick de Vos ◽  
Nikolaos M. Papadakis ◽  
Georgios E. Stavroulakis
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Acoustic Measurements ◽  
Frequency Range ◽  
Acoustic Parameters ◽  
Source Characteristics ◽  
Sound Levels ◽  
Engineering Practices

A handclap is a convenient and easily available source for room acoustic measurements. If used correctly (e.g., application of optimal hand configuration) it can provide usable results for the measurement of acoustic parameters, within an expected deviation. Its biggest drawbacks are the low sound pressure level (especially in the low frequency range) as well as its low repeatability. With this in mind, this paper explores the idea of testing a handclap with a glove in order to assess the effect on its source characteristics. For this purpose, measurements were performed with 12 participants wearing leather gloves. Sound levels were compared with simple handclaps without gloves, and between grouped results (overall A-weighted SPL, octave bands, 1/3 octave bands). Measurements were also performed several times to evaluate the effect on repeatability. Results indicate that the use of leather gloves can increase the sound levels of a handclap by 10 dB and 15 dB in the low frequency ranges (63 Hz and 125 Hz octave bands, respectively). Handclaps with leather gloves also point toward improved repeatability, particularly in the low-frequency part of the frequency spectrum. In conclusion, compared to simple handclaps without gloves, evidence from this study supports the concept that handclaps with leather gloves can be used in engineering practices for improved room acoustic measurements of room impulse response.

Stable Method for Active Cancellation of Duct Noise by Synthesized Sound

1987 ◽  
Vol 109 (1) ◽  
pp. 37-42 ◽  
Author(s):  
K. Kido ◽  
S. Morikawa ◽  
M. Abe
Keyword(s):  
Transfer Function ◽  
Impulse Response ◽  
Sound Pressure ◽  
Noise Cancellation ◽  
New Method ◽  
Wave Form ◽  
Frequency Range ◽  
Stable Method ◽  
Active Noise ◽  
Active Cancellation

This paper describes an active noise cancellation system utilizing computer-synthesized sound. This computer-synthesized sound is generated by using a new method to estimate the impulse response of a system involving inverse transfer function of a loudspeaker. A loudspeaker is set close to the end of a duct to radiate sound for cancellation. The loudspeaker is driven by a signal which is synthesized by convoluting the estimated impulse response and the wave form of a noise picked up by a microphone set in the duct. The system is substantially stable. In our experiment, using a duct 8.5 m in length, the sound pressure at a point outside the duct is decreased by about 3 to 8 dB over a frequency range between 50 Hz and 200 Hz.

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