“多边形膜片”传声器音质分析

对一组膜片为多边形的大振膜录音传声器进行客观测量与主观音质评价,探讨膜片的形状对客观参数和主观听感的影响,为设计具有特性听感的录音传声器提供依据与参考.结果表明,正八边形膜片传声器的主观音质综合表现较好.     

钢琴幅度谱的七、九次谐波对钢琴音质影响的研究

主要研究了钢琴声音幅度谱中的第七、第九次谐波对钢琴音质的影响。重点考察了衰减第七、第九次谐波幅度情况下，钢琴声音音质的变化情况。实验结果表明，在钢琴的中低音区，不论是单键发音，还是三度和声、五度和声或三度和弦，令第七、第九次谐波的幅度衰减，均能使钢琴声音的音质有所改善。但如果衰减幅度太大，反而会使得钢琴的声音更加单薄。因此，中间应存在一个最佳比值，这个比值有待进一步的研究。     

5种环绕声拾音方法空间特性的主观评价实验

为得到不同拾音制式在空间感塑造上的差别,对5种常用的环绕声拾音方法进行主观评价实验,得到各拾音方法在5个空间特性参量上主观心理尺度值,总结出拾音制式中传声器布放对空间特性的影响规律。运用环绕声录音和重放原理,结合对重放声双耳互相关系数测量的数据,对结论进行了分析和讨论。     

小型扬声器感知低音的生成算法优化

虚拟低音技术针对扬声器低频重放问题提供了一种较好的处理方式,其建立在“虚拟音高”理论基础上,将扬声器输入信号在不能重放的低频部分利用其高次谐波成分在听感上虚拟出基频音高.考虑到小型扬声器频带窄、失真大等特性,在虚拟低音的相位声码器算法基础上,用二阶求导的方式对频谱低频峰值进行取点,对不同频段生成不同的谐波个数,简化幅度控制,提出适合于小型扬声器的低音谐波生成模块优化算法并实现.主观实验结果表明改进后的算法在增强低音效果的同时也能保证较好的整体音质效果.     

击弦点及击弦力度对钢琴幅度谱的影响

从理论和谱分析实验研究了钢琴的击弦点及击弦力度对钢琴幅度谱的影响。首先通过弦振动理论对速度振幅进行了理论计算，然后用计算机对钢琴的原始录音进行分析和处理，得出了钢琴的幅度谱，最后讨论了击弦点及击弦力度对钢琴幅度谱的影响。结果表明，虽然钢琴的幅度谱值与速度振幅值之间不存在简单的对应关系，但两者是成正比的。欲改变各次谐波幅度谱值之间的比例关系，可以比较方便地通过调整A/L值来达到。     

古典音乐录音中空间环境感的处理

本文回顾、整理了听觉空间环境感的概念和古典音乐同期录音拾音设计方案,结合三场交响音乐会的实践经历,对使用不同拾音方案录制的音乐作品进行主观评价及声学原理分析,从主传声器与辅助传声器拾音设计的两个方面探索古典音乐同期录音中空间环境感的处理经验。     

声学头模双耳录音听感效果分析

对比分析了仿真头模录音与简化声学头模录音的听感效果。选择水平面以45°为间隔的8个方向进行录音,通过听感实验判断双耳录音的方向定位正确率以及头中定位的情况。结果表明,声学头模与仿真头模在听感定位上没有显著性的差别,在双耳录音及一些其他场合可采用简化声学头模来代替仿真头模。     

电池供电的FET甲类6W功放

用蓄电池供电的功率放大器具有音色透明、真实的特点。本文介绍的功率放大器采用两组蓄电池分别为左右声道独立供电,排除因共用一组蓄电池而使音质受电池内阻、馈线电阻等公共阻抗的影响,因而音质得到进一步提高。在电路中通过负反馈电路提高低频分量,克服了听感上低音不足的缺点。     

高保真扬声器系统设计的探索

综合利用客观的测量结果、计算机模拟分析结果和主观的听感音质评价结果,进行了一个二分频高保真扬声器系统的设计。探索以主观听感的艺术性要求去进行高保真扬声器系统的技术性设计,追求艺术与技术的相互结合。     

声景素材的听觉感知差异研究

用不同录音方式采集的环境声音存在听觉差异。随着三维声的逐渐流行，选择何种录音方式用于三维声节目的声景素材采集需要进行对比研究。为此，介绍一项针对全景声节目声音素材采集的对比实验。使用双耳录音方式、XY制式立体声录音方式、单声道录音方式录制声音样本，经过调制后进行耳机听音测试。来自23名普通听音员的听音感知报告显示，双耳录音样本与经过调制的立体声录音样本听感无显著差异，经过调制的单声道录音样本与前两项样本之间存在显著听感差异。专业录音员的主观报告认为，三份样本之间存在差异，主要体现在声音细节和空间感方面。     

Discriminative tonal feature extraction method in mandarin speech recognition

To utilize the supra-segmental nature of Mandarin tones, this article proposes a feature extraction method for hidden markov model (HMM) based tone modeling. The method uses linear transforms to project F0 (fundamental frequency) features of neighboring syllables as compensations, and adds them to the original F0 features of the current syllable. The transforms are discriminatively trained by using an objective function termed as "minimum tone error", which is a smooth approximation of tone recognition accuracy. Experiments show that the new tonal features achieve 3.82% tone recognition rate improvement, compared with the baseline, using maximum likelihood trained HMM on the normal F0 features. Further experiments show that discriminative HMM training on the new features is 8.78% better than the baseline.     

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.     

一种基于频率特征及动态窗长的钢琴调音算法

时域分析法是一种基本的语音分析方法。由于钢琴乐音模型与语音模型相似,故语音时域分析法可被用于钢琴乐音分析中。提出一种基于频率特征及动态窗长的钢琴基音识别时域算法,该算法能根据检测目标设计更为合适的分帧加窗模式,经过实验,可有效地提高检测精度及速度,在钢琴调音及单乐音基音识别应用中具有推广意义。     

多媒体钢琴标准音发声器

提出了一种利用多媒体计算机组成的钢琴标准音发生器,利用声卡可产生对应于钢琴１－８８键基音的标准音,而显示器则显示相应的界面,通过鼠标或外接脚踏开关可对发生器进行控制和操作。该发生器可用于钢琴的音准调整。     

Progress Tones in PCM Switching Environment

This correspondence defines a new set of precision tone frequencies for digitally generating normal progress tones in a PCM switching environment. The technique of generating the progress tones is similar to the one described for digital multiple frequency (MF) tone senders in which the tone is generated by reading a memory store that contains the binary words representing a presynthesized waveform [1]. New frequency combinations are derived that minimize storage requirements by taking advantage of the allowable frequency tolerances to force waveform symmetry with respect to the sampling period.     

Tone mapping with contrast preservation and lightness correction in high dynamic range imaging

In real-world environments, the human visual system perceives a wide range of luminance in a scene. However, the full range of tones in a high dynamic range (HDR) scene cannot be displayed on standard display devices due to their low dynamic range (LDR). Therefore, tone mapping is necessary to faithfully display a HDR scene on an LDR display device. Existing tone mapping methods have problems because details and contrast in a scene are not preserved faithfully, and they also distort the colors in a scene. Thus, we propose a tone mapping method for preserving the detail in an HDR scene using a weighted least squares filter, which preserves the global contrast in a scene by using a competitive learning neural network, before applying a tone reproduction operator to preserve the color without shifting the lightness. According to the Helmholtz–Kohlrausch effect, the perception of brightness depends on the lightness, chroma, and hue of a color. For example, the luminance of pixels with specific colors such as red and blue is low in an HDR scene. The proposed method corrects the lightness of pixels according to the color (i.e., lightness, chroma, and hue) of a tone-mapped image. Experimental results with several test sets of images demonstrated that the proposed tone mapping method with contrast preservation and lightness correction is more suitable for dynamic range compression than existing tone mapping methods, while it also preserves the color of a scene in an effective way.     

基于Multisim八音阶电子琴的设计与仿真

介绍了以RC串并联选频网络为主振电路的电子琴设计方法,给出了八音阶电子琴电路参数的设计方法和一组参数值。并采用Multisim10对RC串并联正弦波振荡电路进行了设计仿真。结果证明,用模拟电路方法制作电子琴结构简单,而且成本低廉,符合C音调基准音标准。     

The tone sense multiaccess protocols with partial collisiondetections (TSMA/PCD) for packet satellite communications

The tone sense multiaccess with partial collision detection (TSMA/PCD) protocol is particularly suitable for a packet satellite system serving an area with a dense population of earth stations. By incorporating a narrowband ground radio channel for broadcasting busy ones, the earth stations are able to avoid packet collisions by sensing for the absence of busy tones before transmitting packets. Partial collision detection capability can also be achieved. Single-tone TSMA/PCD gives 97% of the carrier-sense multiaccess with collision detection (CSMA/CD) throughput when N=10 tones are used, while for multitone and slot-by-slot announcement TSMA/PCD protocols only N=8 and N=2, respectively, are sufficient to drive the system to the CSMA/CD performance     

Performance of multitone FFH/MFSK systems in the presence ofjamming

A novel type of diversity signaling for an M-ary frequency-shift keyed modulation format involving the transmission of multiple tones on each diversity branch is considered. The properties of such a system are investigated, and its performance in the presence of tone jamming is analyzed. It is shown that significant gains can be realized with such a technique. The performance in the presence of worst-case partial band noise is briefly considered and shown to be worse than, though comparable to, that of the single-tone case