Microphone Handling Noise: Measurements of Perceptual Threshold and Effects on Audio Quality

A psychoacoustic experiment was carried out to test the effects of microphone handling noise on perceived audio quality. Handling noise is a problem affecting both amateurs using their smartphones and cameras, as well as professionals using separate microphones and digital recorders. The noises used for the tests were measured from a variety of devices, including smartphones, laptops and handheld microphones. The signal features that characterise these noises are analysed and presented. The sounds include various types of transient, impact noises created by tapping or knocking devices, as well as more sustained sounds caused by rubbing. During the perceptual tests, listeners auditioned speech podcasts and were asked to rate the degradation of any unwanted sounds they heard. A representative design test methodology was developed that tried to encourage everyday rather than analytical listening. Signal-to-noise ratio (SNR) of the handling noise events was shown to be the best predictor of quality degradation. Other factors such as noise type or background noise in the listening environment did not significantly affect quality ratings. Podcast, microphone type and reproduction equipment were found to be significant but only to a small extent. A model allowing the prediction of degradation from the SNR is presented. The SNR threshold at which 50% of subjects noticed handling noise was found to be 4.2 ± 0.6 dBA. The results from this work are important for the understanding of our perception of impact sound and resonant noises in recordings, and will inform the future development of an automated predictor of quality for handling noise.

本研究开展了一项心理声学实验，以测试麦克风操作噪声对感知音频质量的影响。操作噪声是同时困扰使用智能手机与相机的业余爱好者，以及使用独立麦克风与数字录音机的专业人士的共性问题。实验所用噪声取自智能手机、笔记本电脑与手持麦克风等多种设备的实测数据。本研究对表征这些噪声的信号特征进行了分析与呈现。受试声音涵盖两类：一是敲击或碰撞设备产生的各类瞬态冲击噪声，二是摩擦引发的持续性声响。在感知实验环节，受试者试听语音播客，并对所感知到的各类有害声音的劣化程度进行评分。研究开发了一套具有代表性的实验设计方法，旨在引导受试者进行日常聆听而非分析性聆听。实验结果表明，操作噪声事件的信噪比（Signal-to-Noise Ratio, SNR）是音质劣化的最佳预测因子。其他因素，如噪声类型或聆听环境中的背景噪声，并未对音质评分产生显著影响。播客内容、麦克风类型与重放设备虽被证实存在显著影响，但影响程度均较为有限。本研究提出了一种可基于信噪比预测音质劣化程度的模型。研究发现，当信噪比为4.2 ± 0.6 dBA时，有50%的受试者能够察觉到操作噪声。本研究成果有助于深化人类对录音中冲击声与共振噪声的感知理解，并将为未来开发操作噪声音质自动化预测工具提供重要的理论支撑。