The Advantages And Problems Of Acoustic Head Recording

- Sep 25, 2018-

The recording evaluation method based on the acoustic head mode refers to placing the acoustic head mold in the audience area or the stage area of the site to be evaluated, using the acoustic head mode to perform binaural recording on the live performance, and then recording the ear with earplugs in the standard listening room afterwards to replay, it is a method of subjective evaluation of the live sound effects of the show. Special attention is required: the position, orientation and height of the acoustic head mode should be consistent with the listener or performer during recording. If speaker playback is used, crosstalk cancellation processing is required for the binaural signal, but this will cause a certain distortion of the sound field and affect the evaluation result. Therefore, speaker playback is not recommended. In order to remove the influence of the electroacoustic system during the recording and playback of the acoustic head mode, it is necessary to perform frequency response equalization of the two micro-microphones and earplugs in the acoustic head mode.

Advantages: The recording method based on acoustic head mode completely solves the limitation of time and region on-site evaluation. Listeners do not need to go to the performance site to evaluate at any time and any place, which greatly saves the listeners. The time and effort also saves money and brings convenience to the evaluation work. In addition, the recording evaluation has complete repeatability, which is convenient for testing the reliability and validity of the evaluation.

The perfect sound effect not only makes the audience get the best listening experience, but also the other actors and other aspects to get higher satisfaction. Therefore, the evaluation of the live sound effect should not only evaluate the audience area (speech clarity, sound field reverberation, intimacy, warmth, fullness, hearing source width, auditory envelopment, sound field naturalness, etc.). The stage area (language clarity, sound field naturalness, time zone response timeliness, etc.) should also be evaluated. In the live performance, the acoustic head model is placed in the stage area for recording, and the sound effect of the stage area can be evaluated. In the same performance, multiple acoustic head models are placed in different positions in the stage area and the audience area for multi-point recording, so that the sound effects at different positions in the hall can be compared in the listening room. These are not possible with traditional on-site evaluation methods.

Problems: As is well known, binaural recordings have problems with before and after sound image confusion and sound in the head. At present, there are many ways to improve this kind of sound image distortion to a certain extent. Most of the methods are signal processing on binaural recording or HRTF, increasing the difference between the spectrum before and after, and enhancing the auricle effect to distinguish the front and rear sound images. . However, the signal processing of the binaural recording will cause the restored sound field to be distorted to some extent. The most important thing is that the change in the tone will seriously affect the subjective evaluation result. Another effective method is to add the dynamic factor of the head, which better solves the problem of confusion before and after the sound image in the head. However, the head dynamics can only be added to the virtual environment created by the binaural signal synthesis technology, and the HRTF used for the synthesis needs to be changed in real time according to the listener's head motion. During the binaural recording process, the acoustic head mode is kept fixed and dynamic factors cannot be added. Therefore, this improvement method is not applicable to the live sound effect recording evaluation based on the acoustic head mode.

 

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