基于SeeSV噪声定位技术的电机噪声测试

针对驱动电机某一运转工况的噪声声压级与电机噪声频率的测试问题,提出了一种运用声学照相机SeeSV与传声器相结合,并同时检测电机振动信号的测试方法。通过选取SeeSV的不同频段对噪声源进行定位识别,分离出驱动电机的噪声频段,运用传声器测定电机的噪声强度,并用振动信号对声压信号进行验证。测试结果表明,用SeeSV和传声器相结合的方法,可在复杂噪声中识别出驱动电机的噪声频率为2 66625 Hz,声压级为607 dB,对工程噪声的评价具有实践意义。     

A Neuromorphic Sound Localizer for a Smart MEMS System

In this paper we present an analog circuit that determines the direction of incoming sound using two microphones. The circuit is inspired by biology and uses two silicon cochlea to determine the azimuthal angle of the sound source with respect to the axis of the two microphones using the time difference between the two microphone signals. A new algorithm, adapted to an analog VLSI implementation, is presented together with simulation and measurement results.     

不同传声器拾取男女语声的频率响应对比分析

通过阐述不同类型常用传声器的性能特点,采用实验的方式,分析男女语声的频谱结构.实验中,使用插件来记录各传声器对于男女语声的频率响应,将得到的数据绘制成频谱图,以此来比较不同传声原理及振膜尺寸的传声器在拾取男女语声后的重放频响.同时,与汉语普通话的平均频谱及元音的共振峰频谱图进行比较,对四类传声器在男女语声的重放音质上做...     

基于MSP430的声音定位系统的设计

声源定位在当今日益智能化的社会中有着诸多方面的应用,特别是在智能控制,军事等领域。文中设计的系统以MSP430F449单片机为控制核心,步进电机驱动的小车作为移动声源载体,设计两个间距固定的麦克风作为接收设备,测量声源发声到麦克风接收到声音的时间差数据,声源通过无线模块接收到数据从而计算出声源的坐标,然后控制声源小车运行到指定坐标实现定位控制。经测试,本系统能精确的控制小车到达指定坐标点,系统工作稳定。     

Study of structural noise owing to nonlinear behavior of capacitive microphones

This paper deals with the study of structural noise in a capacitive MEMS microphone, which consists of a fully clamped circular micro-plate. The micro-plate is subjected to a bias DC voltage and sound pressure waves. Due to the nonlinearity and displacement dependency of the electrostatic force, the amplitude of the applicable bias DC voltage has some limitations and also this nonlinearity causes the generation of super or sub-harmonic responses and consequently the initiation of the structural noise in capacitive microphones. In order to determine the amplitude of the generated structural noise in these microphones, the first order multiple scales method is used and asymptotic analytical solution of the dynamic response is presented. The effects of the bias DC voltage value on the fundamental frequency, sensitivity and consequently on the amplitude of the structural noise of the microphone are studied. In addition the effects of the sound pressure frequency and amplitude on the value of structural noise are investigated.     

Robust sound localization in 0.18 /spl mu/m CMOS

This paper presents a hardware implementation of a sound localization algorithm that localizes a single sound source by using the information gathered by two separated microphones. This is achieved through estimating the time delay of arrival (TDOA) of sound at the two microphones. We have used a TDOA algorithm known as the "phase transform" to minimize the effects of reverberations and noise from the environment. Simplifications to the chosen TDOA algorithm were made in order to replace complex operations, such as the cosine function, with less expensive ones, such as iterative additions. The custom digital signal processor implementing this algorithm was designed in a 0.18-/spl mu/m CMOS process and tested successfully. The test chip is capable of localizing the direction of a sound source within 2.2/spl deg/ of accuracy, utilizing approximately 30 mW of power and 6.25 mm/sup 2/ of silicon area.     

基于高斯短时分数阶Fourier变换 的海面微动目标检测方法

海上目标随海面颠簸导致姿态变化,引起回波功率调制效应,导致回波多普勒体现时变和非平稳特性.为此,本文将微多普勒理论应用于海杂波中弱目标检测,提出一种基于高斯短时分数阶Fourier变换(GSTFRFT)的海面微动目标检测方法.首先,建立海面目标的平动和三维转动回波模型;然后,基于海尖峰判别方法对回波信号进行数据筛选,改善信杂比,并采用GSTFRFT对微动信号进行增强处理,利用海面目标与海杂波的微动特征差异设计恒虚警检测方法;最后,通过GSTFRFT域滤波,提取信号的微动特征并得到瞬时频率.实测雷达数据仿真结果验证了算法的有效性,具有在强海杂波中检测微弱目标的能力.     

Narrowband auscultatory blood pressure measurement

Auscultatory blood pressure measurement uses the presence and absence of acoustic pulses generated by an artery (i.e., Korotkoff sound), detected with a stethoscope or a sensitive microphone, to noninvasively estimate systolic and diastolic pressures. Unfortunately, in high noise situations, such as ambulatory environments or when the patient moves moderately, the current auscultatory blood pressure method is unreliable, if at all possible. Empirical evidence suggests that the pulse beneath an artery occlusion travels relatively slow compared with the speed of sound. By placing two microphones along the bicep muscle near the brachial artery under the occlusion cuff, a similar blood pressure pulse appears in the two microphones with a relative time delay. The acoustic noise, on the other hand, appears in both microphones simultaneously. The contribution of this paper is to utilize this phenomenon by filtering the microphone waveforms to create spatially narrowband information signals. With a narrowband signal, the microphone signal phasing information is adequate for distinguishing between acoustic noise and the blood pressure pulse. By choosing the microphone spacing correctly, subtraction of the two signals will enhance the information signal and cancel the noise signal. The general spacing problem is also presented.     

话筒在电视制作中的选择和使用

电视节目制作中声音质量的好坏，直接影响电视节目的质量。要保证电视节目声音的质量。必须正确地选择和使用话筒。讨论常用话筒的选择、使用以及影响声音质量和解决方法等问题。     

节目制作中话筒的合理选用

声音的拾取要靠话筒,为了各种收音工作的需要,话筒产品种类繁多,所以节目制作中应综合考虑声源、环境等因素,合理选择与使用话筒.     

Time-frequency analysis of skeletal muscle and cardiac vibrations

Skeletal muscle and the heart vibrate during contraction producing nonstationary signals whose time-varying frequency reflects dynamic changes in physiological properties. Consequently, pathological changes in the mechanical integrity or loading of skeletal muscle or the heart can be expected to alter their vibrations. Classic frequency analysis techniques have been inadequate to characterize these subtle changes because of rapidly varying frequency components. A poor understanding of heart and muscle sound generation has also limited investigations. This paper demonstrates how time-frequency (TF) techniques have illuminated the relationships between muscle/heart material properties and loading and frequency dynamics of heart and muscle vibrations. Studies of evoked twitches from frog skeletal muscle reveal that muscle vibrations occur as transverse oscillations at the muscle's resonant frequency. Using a classic Rayleigh-Ritz model and crude estimates of the muscle geometry, muscle force can be accurately predicted from the muscle sound TF profile. First heart sound vibrations, in contrast, are shown to be a nonresonant phenomena, consisting of propagating transients superimposed upon bulk acceleration of myocardial contraction. Consequently, first heart sound frequency dynamics depend upon cardiac electrical excitation and hemodynamic loading in addition to intrinsic material properties and geometry, necessitating further work to characterize pathophysiologic correlations     

多倍直流偏置电压对碳纳米管薄膜声源的影响

针对碳纳米管薄膜声源系统的输出声信号频率失真问题,提出在交流信号上施加多倍直流偏置电压的方法。从热致发声原理入手,利用碳纳米管薄膜声压理论,分析出增加多倍直流偏置电压后,输出信号中的一倍频与二倍频声压幅值,并探究两者幅值比变化规律。实验结果表明,随着输入频率和直流偏置电压增加,输出声信号中两者幅值之比亦增加,当直流偏置电压是交流电压的两倍后,输出声信号波形与输入电信号近似一致,较好地解决了频率失真问题;同时,输出声压级也有较大幅度提升。     

TDOA声源定位中阵列阵型对误差的影响

在麦克风阵列声源定位中,不同阵列阵型及声源频率高低均对定位结果产生影响,探讨上述不同变量对定位结果产生误差的定量分析。使用到达时间差测量(TDOA)算法,运用16个麦克风分别组成十字型、同心圆、方型、L型、Y型阵列,探讨不同形状的麦克风阵列在不同频率声源下所产生的定位误差,并在Matlab上进行仿真分析,尝试得到较为准确的声源定位结果,提出一种误差最小的用于麦克风阵列声源定位的同心圆阵列阵型。     

The active control of sound

Active control of sound results from destructive interference between the sound field of an original acoustic source and that from a controllable array of `secondary' acoustic sources. For this destructive interference to occur over an appreciable region of space the sound field of the secondary sources must match that from the primary source in both time and space. The spatial matching requirement leads to an upper frequency of applicability of active control. Active control complements conventional passive methods of sound control, which do not work well at low frequencies. Practical feedforward controllers, using a multichannel generalisation of the well known LMS adaptive algorithm, have been developed, using as many as 16 loudspeakers and 32 microphones, and applied with considerable success in the control of low-frequency propeller noise inside aircraft and low-frequency engine noise inside cars. The authors describe such systems     

The Plenacoustic Function and Its Sampling

The spatialization of the sound field in a room is studied, in particular the evolution of room impulse responses as a function of their spatial positions. It was observed that the multidimensional spectrum of the solution of the wave equation has an almost bandlimited character. Therefore, sampling and interpolation can easily be applied using signals on an array. The decay of the spectrum is studied on both temporal and spatial frequency axes. The influence of the decay on the performance of the interpolation is analyzed. Based on the support of the spectrum, the number and the spacing between the microphones is determined for the reconstruction of the sound pressure field up to a certain temporal frequency and with a certain reconstruction quality. The optimal sampling pattern for the microphone positions is given for the linear, planar and three-dimensional case. Existing techniques usually make use of room models to recreate the sound field present at some point in the space. The presented technique simply starts from the measurements of the sound pressure field in a finite number of positions and with this information the sound pressure field can be recreated at any spatial position. Finally, simulations and experimental results are presented and compared with the theory.     

基于小波和分形理论的调制信号特征提取方法研究

本文针对通信信号这种非平稳的、信噪比(SNR)变化范围较大的信号,应用小波分析和分形理论,提出了有效的特征提取方法,所提取的分形特征包含了区别不同调制类型所需的幅度、频率和相位等主要信息。同时这种特征具有较好的抗干扰特性,基于这种特征的分类器的设计简单、高效。计算机模拟结果表明此方法的有效性。     

用于窄带声源定位的时延估计算法研究

提出了声源为窄带信号时,用一维麦克风阵列所得数据进行时延估计的算法。将由麦克风阵列采集,并通过窄带滤波器的声源信号建模为窄带信号;通过分析其频谱特征,定义了关于信号传至相邻麦克风时间差的搜索函数,以得出所求时延。对于含有背景噪声的情况,在白噪声环境下,用所得数据向量构造Hankel矩阵,通过奇异值分解法去噪;当存在窄带噪声时,用Chebyshev I低通滤波器构造出带通滤波器,达到去噪目的。最后,给出了实验仿真结果,验证方案的可行性。     

EVAM: an eigenvector-based algorithm for multichannel blinddeconvolution of input colored signals

A new algorithm is proposed for the deconvolution of an unknown, possibly colored, Gaussian or nonstationary signal that is observed through two or more unknown channels described by rational system transfer functions. More specifically, not only the root (pole and zero) locations but also the orders of the channel transfer functions are unknown. It is assumed that the channel orders may be overestimated. The proposed algorithm estimates the orders and root locations of the channel transfer functions, therefore it can also be used in multichannel system identification problems. The input signal is allowed to be nonstationary and the channel transfer functions may be a nonminimum phase as well as noncausal, hence the proposed algorithm is particularly suitable for applications such as dereverberation of speech signals recorded through multiple microphones. Several experimental results indicate improvement compared to the existing methods in the literature     

Microwave Transmission through Normal and Tumor Cells

The role of standing waves in the microwave measuring systems used in the study of normal and tumor cells is discussed. A pronounced cyclic variation in measured power as a function of frequency through biological materials has been reported in curves published for two frequency ranges 66-76 GHz and 76-86 GHz. The materials studied included a variety of normal and tumor cells and compounds such as guanine and guanylic acid. A condition for cyclic and multiple resonances in a waveguide system is satisfied when at least two impedance discontinuities giving rise to reflections are present. When we have only two discontinuities, the distance between them may be calculated from the operating frequency and the separation between frequencies for maximum power transmission through a branch of the measuring system. In the resulting standing-wave pattern, the effect of introducing the organic or biological sample with losses over a wide frequency range into the measuring system is to reduce the magnitude of the maxima in the standing-wave pattern and to increase the magnitude of the minima. To distinguish between Iosses due to the sample and the frequency selectivity of the microwave measuring system, one sound procedure is to adjust the system for unity standing-wave ratio (SWR). After this is done, if one still observes a frequency-dependent absorption which arises on introducing the sample or by use of a comparison method employing two samples, the results will no longer be ambiguous. The ambiguity in results reported in the literature will be resolved when effective methods are used to control the frequency selectivity of the equipment.     

双传声器指向性噪声消除在手机中的应用

介绍了一种手机中使用的指向性双传声器噪声消除系统.系统采用两个灵敏度一致性较好的全指向性传声器,形成锥形指向性拾音波束,只接收120.范围以内的信号,大大减少拾音波束之外的噪声干扰;紧接着使用单通道语音增强算法,可进一步衰减采集到信号中的背景噪声.实验结果表明,该系统在保持了较小的语音失真的前提下,对于各种类型的背景噪...