Acoustic optimisation of indoor environments is an interdisciplinary issue related to room acoustics, psychoacoustics, architecture, psychology, sociology and audio engineering. Knowledge of the design factors that lead to certain subjective judgements of perceived quality is increasingly valuable in a community that is concerned by trade-offs between life quality, environment complexity and cost. The research in this field aims to identify the relationships between measurable parameters of room acoustics, background noise, sound signals carrying information, emotions and the subjective responses they elicit in human recipients as well as its effects upon performance and stress. The quality of the spatial attributes of sound is also a significant factor in overall sound quality.

The sound quality of good indoor environments can be of very high standards. However, in many situations the acoustic quality is far from acceptable. Typical problems are high background levels, to high activity levels, inappropriate masking properties (privacy), and not optimised reverberation times, wrong ratios between direct and reflected sound energies, etc. This presentation focuses on relationships between quality aims and technical means. This requires a clear understanding of the relationship between acoustical characteristics in terms of room acoustics, binaural hearing, speech perception, psycho acoustic quantities and spatial attributes of sound, and its relation to a specific context and application. Some basic aspects of good acoustic design and a number of measurement quantities and models relating to the acoustic quality of indoor environments will be presented and discussed. For example: Room acoustic properties and planning regarding absorption, diffusion and appropriate reverberation times; Psycho acoustic quantities like Loudness, Tonality, Fluctuation strength; Acoustic quantities like impulse response and transfer functions, Clarity and Speech Transmission Index.  Two types of “Auditory Brain Models” will also be discussed. One defined by Ando et al, based on auto correlation functions (ACF) and interaural cross correlation functions (IACC), which can describe primitive sensations and spatial sensations by temporal and spatial factors extracted from the ACF and IACF, respectively. Another model is the auditory-scene analysis (Blauert et al), which results in a binaural-activity pattern related to inter aural time and level differences (ITD and ILD). These results in combination with models of harmonicity, attack time, frequency and amplitude modulation can be used for analysis of real environments. Finally, benefits and problems in case of auralization of room acoustics by commercially available soft wares like CATT or Odeon will be discussed. Special attention is on the effects of head-related-transfer-functions (HRTF) identical or similar to the listeners own HRTF: s and source directivity.