Instrumental Assessment of Near-end Perceived Listening Effort
Communication in noisy situations may be extremely stressful for the person located at the near-end side. Since the background noise is originated from the natural environment, it cannot be reduced for the listener. Thus the only possibility to improve this scenario with support of digital signal processing is the insertion of speech enhancement algorithms in the down-link direction of terminals. So far no measurement technique is available to evaluate the impact of signal processing like so-called „near-end listening enhancements“ (NELE), artificial bandwidth extension or additional noise reduction. For mobile phones, acoustic testing in down-link direction is always carried out in silence condition. However, in several state-of-the-art devices, these enumerated algorithms are already included. This implies that a device may behave differently under noisy conditions than in silence, e.g. since NELE algorithms may be triggered by a certain noise level and/or spectrum. Whenever speech processing is inserted into a conversation, quality aspects must also be regarded. A satisfactory balance between speech quality and listening effort is desirable from the user’s point of view. This includes that any down-link signal processing should presume a minimum quality, depending on the environmental noise respectively on the current signal-to-noise ratio (SNR). Auditory experiments addressing these topics can be used to develop a new instrumental method for the evaluation of down-link signal processing. This contribution presents a proposal for the prediction of listening effort as a first step.