一种吸油烟机声品质满意度分级限值评定方法

声品质作为一种描述吸油烟机噪声听觉感知特性的手段已经被行业所接受,团体标准T/CAS 341–2019《吸油烟机噪声声品质测试方法》给出了吸油烟机声品质测试与建模方法,同时通过声品质指数给出了声品质的数值化表达.该标准为各厂商定量描述声品质提供了依据,但目前仍缺乏对产品声品质满意度级别的划分方法,这不利于声品质技术的推...     

Study on the effect of sound duration on the annoyance of helicopter noise by applying a technique of time compression and expansion of sound signals

The number of helicopter operations has rapidly increased during the last 20 years in Japan. Helicopter noise sounds different from other aircraft; the waveform of the sound pressure is impulsive and the signal duration is relatively long. The Environmental Agency of Japan implemented new guidelines for evaluating noise exposure around small airports, including heliports, in 1990. This study was executed in connection with the development of provisional guidelines. Psychoacoustic experiments were carried out to identify an evaluation index for helicopter noise. In order to examine the effect of duration independently, we not only used original sound recordings, but also synthesized sound signals. The durations of these sound signals were time compressed or expanded without degrading the quality of the original sound recording. The test results show that the effect of duration is significant, and that the A-weighted sound exposure level is a better index than the maximum A-weighted sound pressure level for the evaluation of helicopter noise.     

Index for vehicle acoustical comfort inside a passenger car

Sound quality is among the main factors that influence customers’ preference for choosing good automobile products. It all started more than 10 years ago and grows up so fast due to high competition in the automotive industries. A-weighted noise levels and sound power are usually utilised to measure the noise but they are not adequate to characterise the impact sound inside a car. The most popular approach to determine sound quality of a product is to define an annoyance or specific index, which involves both subjective and objective evaluations. Subjective and objective tests should be studied concurrently in order to determine the sound quality inside a passenger car. This approach is used in this paper to evaluate vehicle comfort index according to most frequently used sound quality metrics, namely; Zwicker loudness, sharpness, roughness and fluctuation strength. As a result researchers of different fields of automotive acoustics investigations can use this index according to the type of road (international road roughness) without any need to perform time-consuming jury tests. The metrics are correlated with jury test results that show which of them and how much has affected the acoustical comfort of the vehicle. The relation between road roughness and vehicle acoustical comfort index is another point of interest in this research.     

薄膜型声学超材料对低频振动的隔声特性分析

高效共振混合机工作频率为60 Hz,且系统处于共振,产生较大低频噪声。针对振动机械产生的有害噪声,分析了高效共振混合机低频高加速度共振混合过程的特点,得到了60 Hz低频声波穿透力强的特点,相比传统的以吸声材料构建的50～100 mm厚度、隔声效果小于10 dB的隔声罩,分析了薄膜型声学超材料在低频减振降噪中的隔声特性。通过多物理场仿真分析,60 Hz时隔声量为31.4 dB,确定了硅橡胶弹性薄膜的预应力和质量块的面密度;采用3D打印机快速成型技术,构建了隔声实验装置,分析了独立隔声单元、面密度、薄膜尺寸等隔声特性规律。基于人耳在实际环境中感受到的噪声强度,提出了噪声衰减量和插入损失的分析方法,在距离声源380 mm和1000 mm的位置,60 Hz时隔声量分别为27 dB和38 dB。研究成果丰富了低频隔声特性理论,为薄膜型声学超材料的工程设计和优化提供了技术支撑。     

Improvement of impact noise in a passenger car utilizing sound metric based on wavelet transform

A new sound metric for impact sound is developed based on the continuous wavelet transform (CWT), a useful tool for the analysis of non-stationary signals such as impact noise. Together with new metric, two other conventional sound metrics related to sound modulation and fluctuation are also considered. In all, three sound metrics are employed to develop impact sound quality indexes for several specific impact courses on the road. Impact sounds are evaluated subjectively by 25 jurors. The indexes are verified by comparing the correlation between the index output and results of a subjective evaluation based on a jury test. These indexes are successfully applied to an objective evaluation for improvement of the impact sound quality for cases where some parts of the suspension system of the test car are modified.     

Hartmann phase pick-up method for detection and correction of piston aberrations in a multi-beam coherent combination system

In multi-beam coherent combination laser systems, piston aberration between each sub-beam is often regarded as the dominative factor to deteriorate the combination performance. So as to obtain a favorable combination result, a Hartmann phase pick-up method in combination with a seven-element active segmented mirror is presented to pick up and correct the piston aberrations of a seven-beam coherent combination system. A simulative result indicates that the RMS value of the wavefront can be reduced from 401 nm to 3.7 nm, while the far-field Strehl ratio can be increased from 0.22 to 0.99 after correction.     

听觉感知中的噪声特性语义描述及其分析

基于听觉感知的噪声语义描述是噪声声品质研究的基础性问题,已有研究未将语义描述与噪声来源、频谱特性以及产品运行状态等物理信息联系起来。该文分别针对飞机舱内噪声、车辆噪声和空气净化器噪声这3组典型噪声开展了主观评价实验,并通过多维尺度分析和主成分分析描述了3组噪声的语义空间,系统分析了不同类型噪声的描述词,同时解释了描述词与噪声物理属性之间的联系。研究发现：飞机舱内噪声、车辆噪声以及空气净化器噪声可以由4维、4维和3维语义空间进行描述;不同类型噪声在语义描述中具有共性与个性,3组噪声语义的主要维度均与嘈杂感相关,而噪声的个性描述词与其声源的物理属性密切相关;进行声品质建模及应用时,应同时考虑噪声共性和个性描述词对听觉感知的影响,采取有针对性的措施以提升产品声品质。该文从听觉感知的角度进行了噪声特性的语义描述和分析,研究结果可为产品声品质以及噪声控制研究提供帮助。     

Directional cancellation of acoustic noise for home window applications

This paper focuses on an active noise cancellation system for a home window using a transparent acoustic transducer. In a traditional active noise cancellation system, direct microphone measurements are used for reference and error signals. In the case of the window application, both external and internal sound would be picked up by such microphones. This leads to adverse effects on the performance of the active noise cancellation system and also to distortion of the internal sound. To address this problem, a wave separation technique is proposed to separate the internal and external components of sound. The wave separation algorithm is based on the use of two microphones and an algorithm that separates components based on their direction of travel. An active noise cancellation system is implemented using wave separation for both the error and reference signal measurements. The performance of the resulting ANC system is experimentally tested in a cabin equipped with a window and results are presented. Experimental results show that the new system is able to accurately preserve desired internal sound while cancelling uncorrelated external noise.     

Earmuff comfort

In many industrial and military situations it is not practical or economical to reduce ambient noise to levels that present neither a hazard to hearing nor annoyance. In these situations, personal hearing protection devices are capable of reducing the noise by 20–30 dB. Although the use of a hearing protector is recommended as a temporary solution until action is taken to control the noise, in practice, it ends up as a permanent solution in most cases. Therefore, hearing protectors must be both efficient in terms of noise attenuation and comfortable to wear. Comfort in this case is related to the agreement of the user to wear the hearing protector consistently and correctly at all times. The purpose of this paper is, firstly, to provide some background on the publications related to earmuff comfort, most of which are based on measurement of the total headband force and subjective evaluation using questionnaires. Most of the published results show a weak correlation between total headband force and subjective evaluation. Secondly, this paper presents a new method to measure the contact pressure distribution between the earmuff cushions and the circumaural flesh of the human head and estimate a comfort index. The comfort parameters were investigated and equations developed to calculate comfort indices and overall quality indices. The most important calculated comfort index is measured from the contact pressure distribution and correlated with a subjective evaluation. Measurement results for the pressure distribution of 10 earmuffs show good correlation with the subjective evaluation.     

混合动力车型燃油箱晃荡声的时变响度评价方法与降噪应用

随着市场对汽车舒适性要求的提高,燃油箱油液晃动噪声问题越来越受重视。尤其是对于混合动力乘用车型,由于缺少发动机怠速噪声的掩蔽效应,更容易引起市场用户对燃油箱晃荡声的抱怨。该文以某搭载皮带驱动起动发电机混合动力SUV车型的燃油箱晃荡声问题为案例,系统性地进行了整车测试分析与路径排查工作,结合非稳态的晃动等效动力学模型,阐述了油液晃动瞬时冲击现象的潜在机理,提出了油箱壁面与形貌优化改进的思路;同时,通过对比分析声压级与响度指标方法的差异,说明了采用时变响度声品质指标能够更准确地反映出车内人耳对晃荡声的主观评价感受。该文主要通过“结构声”传递路径的优化,降低了油箱晃动激励到车内的传递,显著改善了车内的油液晃荡声问题,这对提升燃油系统NVH性能集成开发的能力,有着较重要的工程参考价值。     

Existence and analytical predictions of periodic motions in a periodically forced,nonlinear friction oscillator

The grazing bifurcation, stick phenomena and periodic motions in a periodically forced, nonlinear friction oscillator are investigated. The nonlinear friction force is approximated by a piecewise linear, kinetic friction model with the static force. The total forces for the input and output flows to the separation boundary are introduced, and the force criteria for the onset and vanishing of stick motions are developed through such input and output flow forces. The periodic motions of such an oscillator are predicted analytically through the corresponding mapping structure. Illustrations of the periodic motions in such a piecewise friction model are given for a better understanding of the stick motion with the static friction. The force responses are presented, which agreed very well with the force criteria. If the fully nonlinear friction force is modeled by several portions of piecewise linear functions, the periodically forced, nonlinear friction oscillator can be predicted more accurately. However, for the fully nonlinear friction force model, only the numerical investigation can be carried out.     

Research on the procedure for analyzing the sound quality contribution of sound sources and its application

Transfer path analysis (TPA) plays an important role for identifying and quantifying the contribution by airborne and structure-borne in the automotive industry. The main bottleneck of the TPA method is the test time consumption and complex procedure. It becomes a key target in many applications to find out the source with dominant contribution to overall noise rather than to identify each source. In recent years the contribution pattern of sources to the vehicle overall interior noise has changed with the reduction of engine noise, which masks all other sources. The panel radiation noise of vehicle body could not be ignored. There is an increasing demand for analyzing the sound quality contribution of sound sources in simple ways. The procedure for analyzing sound quality contribution of panel radiation noise is suggested in this study, in which an operational path analysis (OPA) method combined with partial singular value decomposition (PSVD) analysis is applied and sound quality objective assessment is introduced. The experimental research for verifying the procedure is finished, from which the source with largest sound quality contribution is picked up from three sources. For engineering application, the sound quality contributions of panels to the interior noise of a micro commercial vehicle are analyzed by using the procedure. By investigating the contributions of sound sources to each sound quality attribute, the dominant sound source is determined.     

Acoustic comfort evaluation in urban open public spaces

This paper presents the results of an intensive questionnaire survey and objective measurements on soundscape, aiming at the evaluation of acoustic comfort in urban open public spaces. From summer 2001 to spring 2002, 9200 interviews were made for four seasons in 14 urban open public spaces across Europe. The results suggest that the subjective evaluation of the sound level generally relates well with the mean L_eq, especially when the sound level is below a certain level, which is 73 dBA on the basis of this study. However, considerable differences have been found between the subjective evaluation of the sound level and the acoustic comfort evaluation: people tend to show more tolerance in terms of acoustic comfort evaluation. The background sound level has been found to be an important index in evaluating soundscape in urban open public spaces - a lower background level tends to make people feel quieter. Analyses of individual sound elements show that the acoustic comfort evaluation is greatly affected by the sound source type - introducing a pleasant sound can considerably improve the acoustic comfort, even when its sound level is rather high. No significant difference was found among different age groups in terms of subjective evaluation of a sound level, whereas in terms of acoustic comfort, there were significant differences.     

Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index R_w along with A-weighted pink noise C and A-weighted urban noise C_tr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.     

流体通过涡激振动机翼的声辐射研究

为了有效地降低涡激噪声,研究了粘性流体通过涡激振动机翼的声辐射。采用Navier-Stokes方程描述二维机翼的流固耦合运动,用弹簧系统代替实际固体变形产生的回复力和力矩,翼型的运动是两个自由度,即垂直于来流的振荡和转动振荡;为了模拟涡激振动,机翼的初始攻角取得比较大,以便产生周期性的旋涡脱落及周期性的流体动力,后者与弹簧系统相耦合,引起振动,用Lighthill声比拟方法研究了由此引起的声辐射。计算结果表明:当涡脱频率和机翼的固有的振动频率一致时,发生锁定的现象,此时的声辐射达到最大。     

A study of active tonal noise control for a small axial flow fan

Sound radiated by a computer cooling fan consists of tones which are phase locked with the rotation, and other less deterministic tones and broadband random noise. This paper demonstrates the feasibility of globally eliminating the rotation-locked tones by applying a very simple destructive interference to a modified cooling fan with the number of struts equal to the number of rotor blades. The rig consists of a miniature electret microphone used as a rotation sensor, an ordinary loudspeaker, and a bandpass filter with adjustable amplitude and phase delay. The microphone is located at the inlet bellmouth of the fan to pick up the fluctuating aerodynamic pressure caused by the passing rotor blades. The pressure spectrum is rich in the blade passing frequency (BPF) and its low-order harmonics. It provides much better performance than a pulse-generating tachometer. Analysis of the original fan noise shows that about 90% of the radiated tonal sound is phase locked with rotation, and this portion is almost completely eliminated in all directions. The reductions of the radiated sound power in the first two BPFs are 18.5 and 13.0 dB, respectively, and the overall sound power reduction is 11.0 dB.     

Measurement of acoustical characteristics of mosques in Saudi Arabia

The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.     

Noise-impact estimates per FTA and APTA criteria

In a recent paper, light-rail line noise exposures were predicted both in terms of maximum pass-by sound levels for comparison to APTA criteria and day-night average sound levels for comparison to FTA criteria. For the local land uses and ambient noise conditions of the project, the distances for the unmitigated pass-by noise exposures to attenuate to the APTA and FTA criteria limits were estimated and the numbers of included dwellings counted. The results found that the FTA impact-onset (i.e., “some-impact”) criterion curve yielded significantly greater noise exposed areas while the APTA criteria yielded results between those of the FTA “some”- and “severe”-impact curves. However, those results only applied to the specific project under evaluation. This paper attempts to extend and generalize the comparison by parametric computation of exposed areas using both the FTA and APTA procedures. Predicted exposures in this paper are compared as a function of background ambient sound levels, type of land use impacted, numbers of daytime and nighttime operations, and train pass-by maximum sound levels. At very low background ambient sound levels, FTA tended to predict the greatest exposure, while in very noisy environments, APTA predicted more exposure. APTA predicted more exposure with low numbers of daily and/or nighttime operations, and FTA predicted more exposure with high numbers, but the comparative exposures were strongly dependent upon background ambient sound level and land use. For train pass-by maximum sound levels, APTA tended to show more exposure for very quiet pass-bys and to be intermediate to FTA/some and FTA/severe for noisier events—with the comparative exposures strongly dependent upon background ambient and land use.