通过测量谐波复合音的基频辨别阈,探讨中等"高次谐波"的音高感知是否依赖于谐波的可分离性,以及掩蔽音对实验结果的影响。实验方法:在目标音单独存在或目标音与掩蔽音混合时,将刺激通过高、中、低三个带通滤波器以获得不同的谐波可分离度。实验刺激设计为5种基频差异和4种相位组合。五名被试均为年轻人,纯音听阈≤15 dB HL。研究结果发现:谐波复合音的基频辨别阈随着信号频段的上移而增大;目标音和掩蔽音的基频差异对基频辨别阈有显著影响;但相位影响不显著。结论:谐波的可分离性对基频辨别阈有显著影响,但中等"高次谐波"的音高感知不依赖于可分离性;混合音的大部分音高感知结果与兴奋模式的峰值大小密切相关。
Fundamental frequency difference limens were measured to study whether pitch perception of medium-rank harmonic complex tones depends on the resolvability of the components and to study the effect of masker tone on discrimination performance.Target tone was presented alone,or mixed with the masker,which were filtered into the same bandpass frequency region(low,medium,or high) to obtain different resolvability.There were five kinds of fundamental frequency difference and four kinds of phase combination between target and masker. Five young subjects participated in experiments,all of whom had normal hearing(thresholds≤15 dB HL).Results found fundamental frequency difference limens were increased with up-shift frequency region of the harmonics.The fundamental frequency difference between target and masker had a significant impact on the performance,while phase effects were small.Analysis suggested that resolvability of harmonics had a significant impact on the fundamental frequency difference limens,but pitch perception of medium-rank harmonics was not based on the resolvability. Analysis also suggested that most results of pitch perception of target-masker mixture were closely correlated with peaks on the excitation patterns.
Directional speech enhancement of signals from microphone arrays is an effective way to improve speech recognition for cochlear implant users.The strict implant size limitation results in a short distance between microphones.The fractional delay problem due to the short distance between microphones is solved by a maximal flat (Maxflat) finite impulse response (FIR) filter,using the Maxflat error criteria at a low frequency containing most of the speech information and energy.The fractional Maxflat FIR filter approximates the ideal digital fractional filter at the magnitude response,phase response,and phase delay characteristics,and is also very low order.The results demonstrate that the Maxflat FIR filter accurately and effectively solves the fractional digital delay and is very suitable for real-time speech processing in practical cochlear implant products.
