Conversion of a head-mounted microphone signal intocalibrated SPL units

A method is reviewed for conversion of a microphone signal into calibrated Sound Pressure Level (SPL) units. The method follows American National Standards Institute (ANSI) standard for S1.4 SPL meters and requires an accurate SPL meter and an accurate calibration sound source for conversion. Accuracy and validation data from test signals and human phonation are provided. The results indicate that under typical speech conditions, an absolute accuracy of plus or minus 1.6 dB (type I SPL meter) can be obtained with a miniature head-mounted microphone.     

三洋摄像机调焦聚焦噪声抑制技术研究

类似数字摄像机的视频采集系统在摄像头缩放或自动对焦时产生较大声噪,回放时主观听觉十分明显.因此需要研究一种抑制一种语音降噪算法,用于消除马达高速旋转引起的可感知机械干扰声噪.本文提出能够平滑调焦和自动聚焦及语音增强的方案.通过改进的鲁棒自适应麦克风阵列方法从带噪信号中恢复语音;同时采用子带后处理法进一步降噪,保证稳定性...     

有距离辨识度的传声器阵列波束优化算法研究*

小尺度线性传声器阵列在便携式通信设备中具有潜在应用前景,其波束优化算法大多关注于抑制来自与声源不同方向的噪声,而不能有效地抑制与声源同方向的噪声。本文通过对几种典型波束优化策略进行改进,增加线性约束条件,使得阵列兼具方向和距离辨识度。论文对比了几种优化方法的波束性能,同时讨论了约束条件对波束旁瓣的影响,并提出了鲁棒性的优化方案。仿真结果显示,合理的优化策略和线性约束条件可以使阵列波束获得很好的聚焦性能。     

一种新型低噪声麦克风前置放大器的设计

传声器集成电路将接收到的麦克风声音信号转换成电流信号,再由前置放大器放大成电压信号。通常,当声音信号很微弱时,放大器放大声音信号时也放大了噪声,造成被放大的声音信号的信噪比很低。对两种电路进行了仿真试验,比较了Claus前置放大器和Eduard CMOS前置放大器的噪声特点。采用0.18μm CMOS工艺进行仿真,分析了电路的噪声频谱密度,提出了一种改进型CMOS前置放大器,有效地改善了前置放大器的信噪比。     

基于任意麦克风阵列的近场声源三维定位算法研究

基于麦克风阵列的声源定位技术在通信、语音处理等领域得到广泛的应用。本文从声音传播的基本原理出发,推导出了精确的相对幅度衰减因子,获得了更加准确的信号传播模型。利用该模型并结合子空间算法的思想,提出了适用于任意拓扑结构的麦克风阵列的近场宽带三维声源定位算法。仿真结果表明,该算法在一维均匀直线阵、二维均匀圆阵和三维均匀球面阵中,均能够得到较好的定位效果。     

传声器阵列语音拾取系统的设计

介绍了传声器阵列语音拾取和传输的基本原理,给出了系统各个模块的设计方案和实现方法。采用FPGA实现多路音频信号复用和传输,完成了大型传声器阵列的结构设计。该系统稳健性能高、扩展性良好、多路语音数据有较高的同步性。在大型互动游戏环境中能方便地完成人机语音指令交互。     

用于调音台的自动混合技术

本文简要地介绍了自动传声器混合技术的原理以及自动传声器混合器必备的功能,并介绍一种国外新近研制成功的自动混合控制器。     

基于近场波束形成的麦克风阵列语音增强方法

当麦克风阵列用于封闭环境中非手持式语音拾取时,必须面对的一个问题是声场为阵列近场的问题。该文在子带自适应波束形成方法的基础上,引进了一种基于近场波束形成的麦克风阵列语音增强方法。该方法充分利用了近场球面波的波前弯曲率,有效地衰减了混响和噪声对期望信号的影响。仿真实验结果表明,在小房间混响条件下,基于近场波束形成的麦克风阵列语音增强方法取得了较好的噪声抑制效果。     

基于波束形成的多类型多声源定位研究

为实现空压机多噪声源的准确定位,仿真对比了多种近场球面波多声源定位算法。基于时域波束形成,研究了相同声源平面、不同声源频率、不同声源纵向距离、不同声源强度下多声源定位以及声源频率、声源纵向距离和声源强度多因素联合的多声源定位仿真方法,模拟了更接近实际的噪声源类型。基于频域波束形成,仿真研究了1400 Hz,2400 Hz,3400 Hz,4400 Hz的多声源。分别利用互功率谱波束形成和除自谱的互功率谱波束形成,仿真研究了相干声源和不相干声源。开发了阵列声成像测试平台,运用频域波束形成和功率谱波束形成对空压机进行了定位试验研究。结果表明,1400 Hz下空压机的主要噪声源是气缸盖、空气滤清器和曲轴附近的机体,这可为空压机减振降噪改进设计提供依据。     

Characterisation of tram noise emission and contribution of the noise sources

The recent expansion of French tram networks and the related local residential complaints mean that a better knowledge of the situations leading to negative reactions from the local inhabitants is required. Hence a research project has been conducted to evaluate and describe noise and vibration emission of trams as well as the perception by the local residents. This paper investigates tram noise emission on common straight track sections, involving two vehicle scales. First the acoustic power and the mean vertical directivity of the total tramset is assessed using an arc of microphones. Then the localisation and the analysis of the main noise sources are performed by means of a cross array during the tram pass-by. Two tram types representing two generations of French rolling stock, both running on two sites with distinct track characteristics, have been investigated considering the effect of speed, tram type, and track type on the noise source contributions and spectral features. Most sources are located in the lower part of the trams, mainly related to rolling noise, with a strong dependence on speed and track type. The tram type dependency, although globally of second importance, influences greatly the noise spectral distribution and behaviour. The HVAC was the only roof-mounted source which could be detected; its contribution towards building storeys becomes significant in configurations of low rolling noise. A tram noise emission model based on the various noise sources has been developed.