precise发病音/持续时间测量？ [英] Precise tone onset/duration measurement?

问题描述

我有，它使用一个FFT以确定特定频率的音（或音对）是否为present中的音频流（如果噪声基底充分高于）一个工作音调检测器。我可以用更多的$ P $有什么方法pcisely找到音的起效时间和持续时间？我寻找的东西远远precise比FFT帧持续时间（约50毫秒）。音调被假定为比FFT帧长得多。

I have a working tone detector which uses an FFT to determine whether a tone (or tone pair) of a particular frequency is present in an audio stream (if sufficiently above the noise floor). What method could I use to more precisely locate the onset time and duration of that tone? I am looking for something far more precise than the FFT frame duration (about 50 ms). The tone is assumed to be much longer than an FFT frame.

推荐答案

如果特定的频率是已知的时间提前，你可以设计围绕频率为中心的带通滤波器，然后只用一个能量检测器的输出。你必须考虑到通过滤波器的大量延时，以及可能还有上升和下降稳态响应的时间。

If the particular frequency is known ahead of time, you could design a bandpass filter centered around that frequency and then just use an energy detector on the output. You'd have to account for the bulk delay through the filter, and probably also the rise and fall times of the steady-state response.

如果您使用的FFT输出实际检测的语气，你有足够的内存，以保持最近的样品，你可以得到从FFT发病的粗略估计，回到过去几百毫秒之前，并开始由正弦在检测到的频率混合样品。然后通过一个低通滤波器运行混合样品。你的音调检测，混频器和低通滤波器的频率分辨率/带宽必须匹配，并再次你需要考虑的LPF特点。

If you're using the FFT output to actually detect the tone, and you have sufficient memory to keep the recent past samples, you could get a rough estimate of the onset from the FFT, go back in time a few hundred milliseconds before, and start mixing the samples by a sinusoid at the detected frequency. Then run the mixed samples through a low-pass filter. Your tone detection, mixer, and LPF frequency resolutions/bandwidths will have to match, and again you'll need to consider the LPF characteristics.

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