Motor Vehicle Exterior Sound Quality Improvement for Indoors

2006 ◽  
Author(s):  
Masao Ishihama ◽  
Hiromitsu Sakurai
Keyword(s):  
Engine Speed ◽  
Motor Vehicle ◽  
Traffic Noise ◽  
Low Frequency ◽  
Sound Quality ◽  
Sound Insulation ◽  
Frequency Range ◽  
Sound Environment ◽  
Frequency Components ◽  
Driving Conditions

The objectives of this study are these three items. 1) To find better indices than dB(A) for representing annoyances caused by motor vehicle traffic noise along highways. 2) To find the frequency range of motor vehicle exterior noise that should primarily be controlled to achieve better indoor sound environment along highways. 3) To find suitable vehicle driving conditions for evaluating indoor sound environment. To obtain the desired results psycho-acoustic experiments were conducted. Firstly, sound samples were collected with microphones placed at such locations as on a sidewalk, in front of a small house and at the center of a room inside of the house. The number of test vehicles was fifteen, consisting of six motorcycles and nine passenger cars. The driving conditions were full acceleration and mild acceleration usually found in normal traffic flow. Secondly, semantic differentiation method was used. Ten pairs of adjectives were used to scale the impressions of each sound sample. Finally, physical characters of the sound samples and their subjective evaluations were compared. The results were obtained as follows. 1) Six sound samples got more uncomfortable impression at indoors. These sound samples were collected by vehicles with sport-type mufflers. 2) The samples that indoor sound quality is degraded than outdoor contain high power in low frequency range below 200 Hz. These low frequency components penetrate through the housing walls more easily than higher frequency components. 3) The degradation of comfort impression was found in mild acceleration conditions. The low frequency components of sound samples for mild acceleration are larger than those for full acceleration. Though the throttle is not fully open in mild acceleration, low engine speed generates low frequency components, and eventually increased indoor sound power in the frequency range. The conclusions drawn from these results are, 1) Indoor sound samples should be included for evaluating sound environment along highways. 2) Mild acceleration is a better driving condition for evaluating indoor sound environment along highways. In this condition, very low engine speed causes low frequency component emission that penetrate into housing more than in heavy accelerating conditions. 3) Engine exhaust systems that emit very loud low-frequency components should be focused upon in regulating traffic noise. 4) Extensive collection and analysis of housing sound insulation, absorption and resonance data along highways are necessary for further investigations. 5) Better psycho-acoustic experiment methods should be developed for investigating sound context effects on panelists.

Investigations on Coherence of Active Control of Traffic Noise Transmission through an Open Window into a Rectangular Room in High-Rise Buildings

2003 ◽  
Vol 34 (8) ◽  
pp. 8-17
Author(s):  
Jiping Zhang
Keyword(s):  
Traffic Noise ◽  
Active Noise Control ◽  
Low Frequency ◽  
Wave Theory ◽  
High Rise ◽  
High Rise Building ◽  
Frequency Components ◽  
Open Window ◽  
Rectangular Room ◽  
Good Agreement

A method for theoretically calculating the coherence between sound pressure inside a rectangular room in a high-rise building and that outside the open window of the room is proposed. The traffic noise transmitted into a room is generally dominated by low-frequency components, to which active noise control (ANC) technology may find an application. However, good coherence between reference and error signals is essential for effective noise reduction and should be checked first. Based on traffic noise prediction methods, wave theory, and mode coupling theory, the results of this paper enable one to determine the potentials and limitations of ANC used to reduce such a transmission. Experimental coherence results are shown for two similar, empty rectangular rooms located on the 17th and 30th floors of a 34 floor high-rise building. The calculated results with the proposed method are generally in good agreement with the experimental results and demonstrate the usefulness of the method for predicting the coherence.

Prediction on Coincidence Effect of Sound Insulation of a Wall

2011 ◽  
Vol 99-100 ◽  
pp. 354-357
Author(s):  
Xian Feng Huang ◽  
Jun Liu ◽  
Yan Yang
Keyword(s):  
Building Materials ◽  
Energy Analysis ◽  
Sound Insulation ◽  
Light Weight ◽  
Statistical Energy Analysis ◽  
Frequency Range ◽  
Single Leaf ◽  
Comparison Results ◽  
Coincidence Effect ◽  
Sound Environment

Coincidence effect which occurs in a certain frequency range will impairs the sound insulation of walls. For the purpose to predict the phenomenon of coincidence effect that is unlikely predicted theoretically by the mass law, the Statistical Energy Analysis (SEA) theory are adopted in studying coincidence effect of sound insulation of the light weight single-leaf wall. The comparison among predicted by SEA, by mass law and measured was performed. Therefore, the comparison results show that sound insulation prediction by SEA is more precise and agrees with the measured date. Moreover, the coincidence effect and its effect on sound insulation were predicted by SEA. Eventually, it is likely to select appropriate building materials and configuration to achieve a better sound environment theoretically.

Investigation on low-frequency broadband characteristics of three-dimensional acoustic black hole superstructures

2020 ◽  
Vol 34 (17) ◽  
pp. 2050151
Author(s):  
Zhuo Zhou ◽  
Xiao Liang ◽  
Jiu Hui Wu ◽  
Peng Shang ◽  
Jiamin Niu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Three Dimensional ◽  
Low Frequency ◽  
Sound Insulation ◽  
Frequency Range ◽  
Multi Stage ◽  
Two Samples ◽  
Acoustic Black Holes ◽  
Frequency Sound Wave

In order to solve the problem of strong penetration and difficult attenuation of low-frequency sound wave in traditional materials, several three-dimensional acoustic black hole superstructures are designed. First of all, multi-stage acoustic black holes are designed. It is found that their sound insulation coefficient is about 0.9 in the frequency range of 50–1600 Hz when the ration of the outlet tip diameter to the inlet diameter is [Formula: see text]. Then, the acoustic black hole thin and light superstructure was designed by embedding many acoustic black hole units in an array on the 10 mm thick plate. The sound insulation coefficient of two samples embedded 81 or 144 acoustic black holes is above 0.96 in the frequency range of 50–1600 Hz. To facilitate processing and engineering applications, we designed acoustic black hole wedge-shaped plate superstructures, and found that the average sound insulation of these acoustic black hole superstructures is 30 dB in the frequency range of 50–1600 Hz. These superstructures will be widely used in anechoic rooms, factories and aviation.

Lung and respiratory impedance at low frequency during mechanical ventilation in rabbits

1995 ◽  
Vol 78 (6) ◽  
pp. 2153-2160 ◽  
Author(s):  
M. Rotger ◽  
R. Peslin ◽  
D. Navajas ◽  
R. Farre
Keyword(s):  
Mechanical Ventilation ◽  
Low Frequency ◽  
Pulse Amplitude ◽  
Sine Wave ◽  
Conventional Mechanical Ventilation ◽  
Frequency Range ◽  
Excitation Signal ◽  
Flow Generator ◽  
Frequency Components ◽  
Difference Criterion

We have tested in eight rabbits the feasibility of measuring respiratory (Zrs) and lung (ZL) impedances in the low-frequency domain, including below the breathing frequency (fb), during conventional mechanical ventilation (CMV). The animals were tracheotomized and ventilated with a tidal volume (VT) of 20 ml at a fb of 1 Hz. The excitation signal was provided by a flow generator connected in parallel with the ventilator; it included six components ranging from 0.45 to 14.8 Hz, which met the neither-sum-nor-difference criterion of B. Suki and K. Lutchen (IEEE Trans. Biomed. Eng. 39: 1142-1151, 1992) to minimize the influence of nonlinearities. Zrs and ZL were also measured at the same mean lung volume and with the same excitation signal both during apnea and when the ventilator signal was replaced by a sine wave with the same VT and fb (SMV). The real parts (Re) of both Zrs and ZL, as well as the effective elastances, were significantly larger during apnea than during CMV and SMV over the whole frequency range. Re(Zrs) and Re(ZL) were similar during CMV and SMV above fb but they were lower during CMV at 0.45 Hz. The latter difference seems to be related to the presence of harmonics of fb and of additional frequency components due to pulse amplitude modulation. We conclude that, because of nonlinearities, it is feasible to measure Zrs and ZL during CMV only at and above fb.

scholarly journals Control the Frequency Response of a Loudspeaker by Changing Its Enclosure

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Pavlo Olehovych Riabokon
Keyword(s):  
Resonant Frequency ◽  
Resonance Frequency ◽  
Frequency Response ◽  
Rock Music ◽  
Low Frequency ◽  
Total Quality ◽  
Frequency Range ◽  
Low Frequencies ◽  
Frequency Components ◽  
Internal Volume

This article analyzes how to control frequency response of a loudspeaker by changing the volume of its closed-box enclosure. The calculation is performed by the method of  Thiele-Small on the basic of a pre-calculated loudspeaker, the parameters of which are given in third section. This became possible because of the simplification of the circuit on figure 1 to the form of circuit on figure 2. This allowed us to consider it as a second order filter (presence of two reactive elements). Obtained results are compared with corresponding characteristics of open-box enclosure of the same loudspeaker, that was pre-calculated by the author too. Results are presented graphically in figure 3 and 4. As can be seen from them, the resonant frequency of the loudspeaker in the closed-box enclosure is higher than the resonant frequency of the loudspeaker in the open box. The result in the form of a ratio  is listed in table 2. Analyzing the obtained data, it can be noticed that with the change of the internal volume of the closed box (and hence its total quality factor), it is possible to affect both the resonance frequency and the peak amplitude values in these frequencies by changing the FR. The result shown in figure 3 and 4 is achieved by taking into account effect of radiation only on the one side of the driver (in the case of open-box enclosure). Closed box was calculating by taking into account both sides radiation of the driver. Shifting the resonance frequency of the system towards higher frequencies and increasing the sound pressure on the resonance generally worsens the FR of the loudspeaker (reduces the reproduction of low-frequency components of sound and increases the unevenness of the frequency). However, certain variants of this group of frequency characteristics may be useful depending on the reproducible frequency range and need of emphasize the low-frequency components (for example, in rock music). If you need a smoothed low-frequency sound, it is appropriate to use systems with low overall quality and increased internal volume or open-box enclosure. Therefore, the volume of the closed-box enclosure significantly affects the resonant frequency and the shape of the frequency response of the loudspeaker. Reducing the volume of the enclosure of the loudspeaker leads to a decrease in its frequency range due to low frequencies and at the same time increase in the unevenness of the frequency response. The change in the resonant frequency of the system as the volume of the closed-box enclosure decreases, the less the volume of the closed-box.

scholarly journals Is the sound environment relevant for how people use common spaces?

2018 ◽  
Vol 25 (4) ◽  
pp. 307-337 ◽  
Author(s):  
Laura Estévez-Mauriz ◽  
Jens Forssén ◽  
Maud E Dohmen
Keyword(s):  
Road Traffic ◽  
Specific Activity ◽  
Traffic Noise ◽  
Sound Quality ◽  
Road Traffic Noise ◽  
Single Attribute ◽  
Sound Environment ◽  
The Difference ◽  
Highly Correlated ◽  
The City

Rapid and intrusive spatial adjustments in common spaces are increasingly questioned by the awareness of citizens demanding higher quality standards. This study aims to understand the use of common space by identifying how the sound environment affects the functions of space and the interaction with other environmental and spatial variables. Is there a certain sound environment required or that should be avoided when designing a space for a specific activity? In situ evaluations with regular users were collected in nine common spaces in Gothenburg, Sweden, conducting sound recordings and questionnaires. Site selection responded to the purpose of the analysed places, the noise level (LAeq) of the city road traffic noise map, and the number of activities suggested by the city sociotope maps. The analyses revealed that certain activities could be identified from LAeq values. Discriminant functions with respect to sound levels primarily identified a tranquil/restorative vibrant dimension, where the highest noise levels tend to be at the most vibrant end. Other results showed that a considerable variability of overall and visual quality judgements came from the variability in sites. These quality assessments were highly correlated, allowing both to be analysed as a single attribute. The variability in sound quality was much lower. Notable is the difference between recorded and perceived loudness. In addition, poor sound quality judgement does not seem to correlate with the perception of mechanical sources as the main source of noise.

scholarly journals AIRBORNE SOUND INSULATION IMPROVEMENT ON MASONRY PARTITIONS USING ADDITIONAL PLASTERBOARD LAYERS

2011 ◽  
Vol 3 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Marius Mickaitis ◽  
Aleksandras Jagniatinskis ◽  
Boris Fiks
Keyword(s):  
Theoretical Calculations ◽  
Low Frequency ◽  
Masonry Wall ◽  
In Situ Measurements ◽  
Sound Insulation ◽  
Frequency Range ◽  
Airborne Sound ◽  
Sound Reduction ◽  
Reduction Index

For the purposes of accumulating knowledge of how to comply with requirements for new buildings of obligatory sound class C or enhanced acoustic comfort sound classes A and B (Lithuanian Building Technical regulations STR 2.01.07:2003), the article discusses improvement on airborne sound insulation of partitions between dwellings using additional plasterboard layers. The results of an empirical approach were obtained performing in situ measurements of the partitions of masonry from silicate blocks and expanded-clay concrete blocks. Theoretical calculations without the evaluation of flanking paths are added. The paper looks at the peculiarities of in situ measurement methods and the estimation of the limiting uncertainty of the sound reduction index. It is showed that the values of the in situ measurements of the airborne sound reduction index in accordance with requirements EN ISO 140 and EN ISO 717 series for rooms having volume higher than 50 m3 varies depending on frequency range. It has been stated, that improvement on the weighed airborne sound reduction index in the frequency range from 100 Hz to 3150 Hz depends on the properties of additional layers and on the characteristics of the main constructions. Resonance in the low frequency range arising due to additional layers may reduce the weighed airborne sound reduction index defined in the frequency range from 50 Hz to 3150 Hz. This fact must be taken into account when designing improvement on masonry wall insulation using an additional layer in dwellings.

scholarly journals Frequency Analysis of Noise Generated by Pneumatic Wheels

2017 ◽  
Vol 42 (3) ◽  
pp. 459-467
Author(s):  
Jan Warczek ◽  
Rafał Burdzik ◽  
Łukasz Konieczny ◽  
Grzegorz Siwiec
Keyword(s):  
Acoustic Emission ◽  
Traffic Noise ◽  
Dominant Frequency ◽  
Frequency Range ◽  
Acoustic Emission Energy ◽  
Measuring Station ◽  
Source Data ◽  
Frequency Components ◽  
Specific Frequency

Abstract The dominant sources of traffic noise, which are linked directly to the vehicle, are dependent on the speed. In terms of speed of 50-120 km/h the dominant source of noise is pneumatic wheels. The aim of the research was chosen to develop a method and experimental determination of the dominant frequency components of noise generated by the car tire. For the purpose of the study and on the basis of the analysis of the source data it was assumed that there is a relationship between the vibration of the tread elements and emitted noise, especially for low and medium frequencies. Thus, the target was set on the basis of the own method of research in the built measuring station. Based on the survey and the obtained results it can be stated that in the spectrum of the noise emitted by the tires the frequency components are dominant. Non-directional tire structure includes more frequency components which at the speed adopted in the studies are located at a greater frequency range than it is for the directional tire. In the case of a tire with a directional tread, acoustic emission energy is more associated with specific frequency components. The developed method provides results independent from the influence of the type of road surface on the acoustic emission while driving.

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