45 years of spatial impression

Abstract

The story of spatial hearing has a certain circularity about it. To date, two separate spatial effects have been identified. The first effect is that created by a reverberant field in an enclosure, which is particularly obvious in a cathedral-type space. A second spatial effect was proposed 45 years ago linked to early lateral reflections. These two are now known as Listener Envelopment (LEV) and Source Broadening (or Apparent Source Width, ASW). Interesting research had been conducted into “Raumlichkeit” in Germany during the '60s. But following the revelations by Marshall, interest in the effects of early lateral reflections overshadowed interest in what is now called LEV. Sound level also contributes to the magnitude of these spatial effects. Measures have been proposed for both ASW and LEV, which include both reflection directional distribution and sound level. The paper will summarise the history of spatial impression and what implications it has for concert hall design. Historical reference: Applied Acoustics (2001) 62, 91-108 and 185-202.