Academic Medical Center, Clinical and Experimental Audiology, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
J Acoust Soc Am. 2012 Oct;132(4):2690-9. doi: 10.1121/1.4747006.
Time-frequency masking is a method for noise reduction that is based on the time-frequency representation of a speech in noise signal. Depending on the estimated signal-to-noise ratio (SNR), each time-frequency unit is either attenuated or not. A special type of a time-frequency mask is the ideal binary mask (IBM), which has access to the real SNR (ideal). The IBM either retains or removes each time-frequency unit (binary mask). The IBM provides large improvements in speech intelligibility and is a valuable tool for investigating how different factors influence intelligibility. This study extends the standard outcome measure (speech intelligibility) with additional perceptual measures relevant for noise reduction: listening effort, noise annoyance, speech naturalness, and overall preference. Four types of time-frequency masking were evaluated: the original IBM, a tempered version of the IBM (called ITM) which applies limited and non-binary attenuation, and non-ideal masking (also tempered) with two different types of noise-estimation algorithms. The results from ideal masking imply that there is a trade-off between intelligibility and sound quality, which depends on the attenuation strength. Additionally, the results for non-ideal masking suggest that subjective measures can show effects of noise reduction even if noise reduction does not lead to differences in intelligibility.
时频掩蔽是一种基于噪声信号中语音的时频表示的降噪方法。根据估计的信噪比（SNR），每个时频单元要么被衰减，要么不被衰减。一种特殊类型的时频掩蔽是理想二进制掩蔽（IBM），它可以访问真实的 SNR（理想）。IBM 要么保留要么去除每个时频单元（二进制掩蔽）。IBM 可以显著提高语音可懂度，是研究不同因素如何影响可懂度的有价值的工具。本研究通过附加与降噪相关的额外感知测量来扩展标准结果测量（语音可懂度）：听力努力、噪声烦恼、语音自然度和整体偏好。评估了四种类型的时频掩蔽：原始 IBM、IBM 的温和版本（称为 ITM），它应用有限和非二进制衰减，以及具有两种不同噪声估计算法的非理想掩蔽（也温和）。理想掩蔽的结果表明，可懂度和音质之间存在权衡，这取决于衰减强度。此外，非理想掩蔽的结果表明，即使降噪不会导致可懂度的差异，主观测量也可以显示降噪的效果。
