Is the X Curve Damaging Our Enjoyment of Cinema

Complaints about poor speech intelligibility and music fidelity in cinema sound tracks persist despite advancements in sound reproduction technology and accreditation of cinema sound systems. The X curve for the equalisation of cinema sound systems has been used for many years and is a foundational element for setting up the tonal balance and achieving accreditation. This paper challenges the acoustic theory behind the X curve, using analysis of acoustic and electro-acoustic measurements made in cinemas and in other spaces where high-fidelity and high intelligibility is required. Both the temporal and tonal developments of the sound field in a number of rooms are examined in detail and related to temporal properties of speech and music and human's perception of tonality.