Development of a Technical Memorandum Describing Optimal Room Acoustic Parameter Ranges for Musical Performance and Rehearsal Spaces

A working group has been convened by the European Acoustics Association to develop optimum Room Acoustic Parameter (RAP) ranges for musical performance and rehearsal spaces. A Technical Memorandum, outlining the proposals of the working group is in production: the main contents are summarized in this article. The main focus has been to develop optimum parameter ranges for concert halls, as well as for other spaces for music rehearsal and performance, such as chamber music halls and orchestra rehearsal halls. It is widely accepted that room acoustic quality is multi-dimensional: multiple RAPs are therefore required to quantify acoustic quality. The RAPs as currently implemented do not however provide a robust differentiation of acoustic quality - both good and bad sounding halls can fall within the RAP ranges currently proposed in the literature. The Technical Memorandum describes a selection process for RAP ranges, with the aim of setting projects on a good path towards acoustical excellence, and to improve the quantification of the outcome. While the possibility to develop novel parameters was at first discussed, is has been agreed that the RAPs already defined in ISO 3382 Part 1 will be used. The RAPs are physically linked; therefore, the RAP optimum ranges must form an internally consistent set, taking into consideration their variation throughout the space. Other important aspects that must be considered in the definition of optimal RAPs that are often overlooked are the orchestra/ensemble size, music type or genre, room volume available, ideal loudness during loud (forte) passages, variation of parameters with acoustic volume and with distance from the source. It has also been established that measurement protocols should be refined to improve the differentiation between spaces of differing acoustical quality

Sam Phillips´ Slap Back Echo : Luckily in Mono

‘Slap back echo’ was created by Sam Phillips for Elvis Presley´s Sun recordingsand later simulated by RCA. Using cepstrum and autocorrelation, wefind that the tape delay used in Sun Studios was 134 - 137 ms, which is solong that the echo is perceived mainly as a distinct echo in the time domain,more than a coloration of timbre in the frequency domain. Even though thedelay time is long, the echo is still perceived as rather “intimate”, because theecho is in mono. Panned in stereo, the feeling of being inside a quite smallroom would disappear. The simulations by RCA, using a hallway instead oftape echo, shows somewhat shorter and less pronounced delays