Monitoring and the environment
Soundtracks are reproduced in various different acoustic environments: the home, the cinema, the conference hall. In an ideal world, all control rooms and listening rooms would be standardized to allow perfect recordings to be made. The Dolby organization provides standards and licences for film rerecording theatres, whereas for small monitoring and mixing spaces the THX organizations analysed the needs and produced their PM3 specifications (Professional Multichannel Mixing and Monitoring).
However, most audio mixing areas are not built to these ideal and exacting specifications, and since sound is very subjective, and no two people are likely to interpret sound in the same way, it is surprising that there is any similarity between recorded sounds at all!