直接辐射式扬声器的非线性研究

扬声器的非线性是影响扬声器音质的一个重要因素,因此,历来都受到有关声学工作者的高度重视。到目前为止,已有好几种测试指标和方法,除了谐波畸变和互调失真以外,还有差频失真、二阶堂失真等,对扬声器的非线性失真的研究,一般只限于高次谐波的产生。本文将扬声器作为非线性振动与辐射系统来研究,提出该器件产生分谐波以至达到混浊状态的一些实验结果,并说明这一现象对扬声器音质的影响是不容忽视的。     

微型扬声器谐波失真分析

总谐波失真(THD)是评价一个扬声器好坏的主要参数,而谐波失真产生的原因是来自于扬声器振膜的非线性振动。针对一类典型的微型扬声器的谐波失真问题进行了研究。首先根据扬声器的结构特点和力学分析建立了振膜非线性振动的数学模型。其次,应用四阶龙格-库塔法和傅里叶变换法给出了此扬声器总谐波失真的数值计算结果。并且采用KLIPPEL声学测量仪器,在消声试验室中测试测得此扬声器样品的总谐波失真数据。总谐波失真的数值计算结果与实验测量值符合较好,佐证了本文理论模型和数值方法的正确性。最后,通过数值模拟讨论了减小扬声器谐波失真优化设计的可能性。     

扬声器大功率谐波失真测量

本文阐述了扬声器大功率谐波失真对于重放音质的影响,指出了它是一个能客观表征扬声器音质的重要参数。问题在于,长期以来人们无法测量这种大功率参数,为此,文中提出了一种使用数字信号处理技术的测量方法,给出了实际测得的几个扬声器大功率谐波失真。最后,文中还介绍了一种微电脑化的扬声器大功率谐波失真仪,它将会在音频界得到广泛的应用。     

基于多相滤波器组的非线性回声抵消

在免提通话系统和移动通信设备中，扬声器常常工作在较高的音量下，容易发生过载现象，从而产生明显的非线性声学回声，这在小微型扬声器中更加常见。常用的线性AEC(Acoustic Echo Cancellation)算法无法消除此类非线性回声，因此通话质量受到严重影响。非线性回声主要表现为额外的高频谐波分量，这些分量使得全带系统不再满足线性关系，而通常的AEC算法都是基于最小化全带误差推导而来，因此性能很容易受到非线性失真的影响。本文提出了一种基于多相滤波器组的子带AEC算法，把全带误差变成了各个子带的误差，因而把谐波失真成分变成了某些子带内的加性噪声，这使得谐波失真较小的那些子带依然能够正常收敛。通过仿真和实测实验，当出现非线性失真时，新方法的ERLE(Echo Return Loss Enhancement)明显高于经典的全带时域和频域方法，对于非线性失真明显的语音信号，ERLE提升约10 dB。      

扬声器谐波失真的改善

简述了电动式扬声器谐波失真的改善方法.通过对音圈设计、支撑系统设计、音盆设计等几个方面的分析,提供了改善扬声器谐波失真的一些参考.     

英国IMPACT现场演出系列扬声器箱

英国Turbosound公司设计并推出了一种现场演出系列扬声器箱，型号为Impact。它应用了创新的设计原理，集专业生产技术及多年现场调音经验，创造出稳固和新式的箱体设计。首先它改进了扬声器箱的单元，使其符合所有扬声器系统的声学指标。现场演出系列使用了专业压缩高音单元，不仅可提供更高的声压和功率，而且其质量更佳。为了解决两路分频的扬声器箱由于只用一个低频分频器作两分频输出导致的失真和音圈发热，以及总谐波失真比例大大升高的问题，Impact现场演出系列将分频点提高了，使高音单元减低了动态性的损害。在这种状况下，中频人…     

基于状态变量分析法的扬声器非线性测试

迄今为止的所有技术都不能动态地测量换能器的某种特定的非线性，并定量地分析其对总失真的影响。失真分析的核心内容是对换能器的非线性进行识别。德国克立佩尔公司成立于1997年。克立佩尔博士研究扬声器15年，建立了扬声器的大信号模型和扬声器非线性的系统识别技术，奠定了对非线性失真进行数字补偿的基础。电动扬声器在大振幅下的表现是不能用线性模型来描述的。     

84A型大功率谐波失真议简介

扬声器大功率谐波失真最能反映重放音质的优劣,长期以来,国内外音频界都想测量达一重要参数而又未能实现。84 A型仪,就是我们根据新近提出的扬声器大功率谐波失真测试原理(见《电声技术》1984年第6期“扬声器大功率谐波失真测量”一文)而独创设计的微电脑化电子仪器。84A型仪内装有多种精密脉冲电路和一整套A/D模数转换—微电路—D/A数模转换数字信号处理系统,它除了能在普通房间里独特地完成扬声器大(小)功率谐波失真测量外,还可兼作同步触发猝发音发生器、双脉冲发生器、矩形波发生器和可调时间窗等仪器使用,从而可与其它仪器组合在一起,完成下列多种声学测量:     

电声元件、器件

0328141扬声器低频谐波跳跃[刊,中]/宗丰德//浙江师范大学学报(自然科学版).—2003,26(2).—131—137(K1)通过能量法求解扬声器非线性震动系统的非线性微分方程的一阶近似解,得出幅频关系方程和谐波失真与频率关系曲线,并着重分析讨论了磁场的非线性对扬声器低频谐波失真跳跃的影响,得出了一些结论。参36     

电动式扬声器单元中的降低失真问题

探讨了在电动式低音扬声器单元中非线性失真的原因,并且提出了减少偶次谐波的带对称磁路的电动式扬声器单元的某些结构方案.介绍了已进行的降低偶次谐波的方法即应用双低频扬声器单元,该方法还能减小声系统箱体的容积.     

Toward Next-Generation Digital Keyboard Instruments

In this article, alternative approaches to digital keyboard instrument synthesis are looked into. Physics-based sound synthesis, which aims at generating natural-sounding musical instrument tones algorithmically without using a large sample database, is a promising approach. It would provide high-quality music synthesis to systems that cannot afford a large memory, such as mobile phones and portable electronic games. The realistic parametric synthesis of musical instrument sounds is still a challenge, but physical modeling techniques introduced during the last few decades can help to solve it. Recently, the first commercial products have been introduced, for example, by Pianoteq. Three keyboard instruments, the clavichord, the harpsichord, and the grand piano, are focused on here. The sound production principles and acoustics of these instruments are first discussed. Then, the previous parametric synthesis algorithms developed for these instruments are reviewed. The remaining part of this article concentrates on new signal processing methods for parametric synthesis of the piano     

有关民族乐器改良的专利现状分析

随着民族乐器的发展以及中西文化的融合,有关民族乐器改进的专利申请量逐年上升。对有关民族乐器专利申请的结构、地域性、申请人、研究方向等方面进行了分析,得到了中国民族乐器改良专利申请具有创造性高度相对较低、地域性明显、申请人以个人为主、民族乐器电声化的特点。通过对有关民族乐器改良的专利现状分析,希望对业内人士有所帮助。     

Enhancing engagement in multimodality environments by sound movements in a virtual space

Since 1959, when electronic music was established as a new way of music composition, the rules of traditional music performance and enjoyment have changed to include space, motion, and gesture as musical parameters. For example, musicians are often located somewhere other than the stage - sometimes even in the audience - and where the music will be performed often influences compositional thinking. Loudspeakers move sound through the space at varying speeds (based on other musical parameters). In addition, the development of live electronics - that is, computers applied to real-time processing of instrumental sounds - has allowed space as a musical instrumental practice to flourish. Electro-acoustic technologies let composers explore new listening dimensions and consider the sounds coming from loudspeakers as possessing different logical meanings from the sounds produced by traditional instruments. Medea, Adriano Guarnieri's "video opera", is an innovative work stemming from research in multimedia that demonstrates the importance and amount of research dedicated to sound movement in space. Medea is part of the Multi-sensory Expressive Gesture Application project (http://www.megaproject.org). Among Medea's intentions, is a desire to establish an explicit connection between sound movement and expressiveness and to show how engagement can be enhanced acoustically in multimodality environments - for example, through the motion of sound through virtual spaces. Whereas sound positioning and movement have seldom been used in concert settings, the ear has great detection capabilities connected to its primary role (a signaling device for invisible or unseen cues); music is now trying to put these capabilities to creative use.     

音箱研讨(六)——闭箱用扬声器的低频参数的调整

首先介绍了闭箱的发展史及其等效电路。重点介绍了几种闭箱用扬声器的设计和参数调整:气垫式音箱用的扬声器设计的7个要点;乐器类扬声器要根据乐器的特式设计。最后列举了两个实例。     

压电扬声器的技术发展及相关专利申请

介绍了压电扬声器领域的技术发展现状。以使用压电材料的不同对压电扬声器的技术特点进行了分别介绍;针对每一种材料的扬声器出现的典型的技术问题,提供相关专利申请的典型代表给出了目前本领域解决上述问题的方案。     

Test signals for music reproduction systems

Experiments with both long, continuous tones and short, transient tones have shown that the human ear is insensitive to relative phase differences between fundamentals and overtones. Short notes from a piano and from a drum are studied here to show that the phase requirement for music reproduction is that the group velocity of the system be constant in the relatively narrow regions surrounding the fundamentals and overtones. The phase velocity across the audio spectrum does not have to be constant, thus easing the requirements on loudspeakers, crossover networks, and tape recorders. Pulse-testing schemes require minimum-phase behavior of a system for simple interpretation and therefore tend to overtest a music reproduction system. Random noise can be used as a test signal if elaborate processing equipment is available. However, the sinusoid is still the best test signal for determining distortion and relating device performance to theory.     

Piezoelectric energy harvesting from vibrations induced by jet-resonator system

Inspired by musical instruments that create high amplitude tones corresponding to resonator acoustic modes when subjected to airflow, a new piezoelectric energy harvester for powering the electronic system of aircrafts is developed. It converts the incoming airflow energy into electricity via a piezoelectric transducer during the flight. With the airflow simulated by an air cylinder, prototypes of the developed energy harvester are fabricated and tested. Experimental results show that the curve of sound pressure, corresponding to the first resonator acoustic mode, is a regular sinusoidal pattern. Within the study range of airflow velocity, a linear relationship can be found not only between sound pressure and airflow velocity but also between open circuit voltage and airflow velocity. A power of above 85 mW is released on a passive electric load of 3 kΩ by using a single piezoelectric element of 10 mm diameter at relative airflow velocity of 159 m/s. And the maximum total energy conversion efficiency of the piezoelectric energy harvester is about 1.2‰. It has laid a solid foundation for powering sensors or other devices, thus eliminating a need for batteries.     

Designing for intimacy: creating new interfaces for musical expression

Contemporary musical instrument design using computers provides nearly limitless potential for designing the mapping between gesture and sound. When designing effective and expressive musical instruments, the types of relationship between musician/player and his instrument and the aesthetics of the relationships must be considered. This paper discusses four types of relationships and their aesthetics. A high degree of intimacy is achieved when the relationship reaches a level where the mapping between control and sound is transparent to the player, that is, the player embodies the device. Ultimately, this type of relationship allows intent and expression to flow through the player to the sound and, hence, create music. Three new interfaces for musical expression, the Iamascope, Sound Sculpting and Tooka, provide examples of how instruments may be designed to develop and explore intimacy and embodiment of new musical instruments.     

光纤传感测振系统的研究

本文报导了一种新型测振装置,用它测量了扬声器的振动特性,不仅得出与传统方法相符的结果,还可得到该法无法测量的其他量,因而为研制扬声器提供一种新的测试手段.     

扬声器的霍夫曼铁定原则及有关讨论

介绍了扬声器的霍夫曼铁定原则,并指出了此原则的意义在于,它表明系统中系统的效率、最低截止频率及箱容积的选取三要素的关联,而且表明了某种物理极限的存在,三要素在扩声用扬声器、HI—FI扬声器和微小型扬声器等体现了不同的搭配。在该原则的限制下如何在产品设计中把握指标间的折衷是产品设计开发中的要点。