The importance of the early reflection portion of a sound decay process in an auditorium is well established. Curves showing early/late sound energy ratios (ELR) in the early reflection period comprise a useful way of examining energy-time data within that period. An auditorium measurement and analysis procedure using ELR data in the period between 20 and 200 ms after the arrival of the initial signal is presented.

Although recent evidence reconfirmed the importance of spectral peak frequencies in vowel identification [Kiefte and Kluender (2005). J. Acoust. Soc. Am. 117, 1395-1404], the role of formant amplitude in perception remains somewhat controversial. Although several studies have demonstrated a relationship between vowel perception and formant amplitude, this effect may be a result of basic auditory phenomena such as decreased local spectral contrast and simultaneous masking. This study examines the roles that local spectral contrast and simultaneous masking play in the relationship between the amplitude of spectral peaks and the perception of vowel stimuli. Both full- and incomplete-spectrum stimuli were used in an attempt to separate the effects of local spectral contrast and simultaneous masking. A second experiment was conducted to measure the detectability of the presence/absence of a formant peak to determine to what extent identification data could be predicted from spectral peak audibility alone. Results from both experiments indicate that, while both masking and spectral contrast likely play important roles in vowel perception, additional factors must be considered in order to account for vowel identification data. Systematic differences between the audibility of spectral peaks and predictions of perceived vowel identity were observed.

The measured 50-ms early-to-late sound energy ratio, C50, is one of the indices used to quantify speech intelligibility in enclosed spaces. A calculated C50 could be useful for predicting intelligibility in hypothetical situations for both unamplified speech and speech reinforcement systems. The equation used for the C50 calculations may also be used for source-directivity evaluations.

Sound energy ratios in one form or another have long been used to quantify and predict clarity. Recognizing the critical importance of early reflections in the sound-decay process to room acoustic character, curves showing early/late ratios in the 20- to 200-ms period may be used as a way of examining the early reflection period, besides providing the established clarity ratings of C50 and C80. An automated measurement program producing octave-spaced energy-time curves and displays of the associated early/late sound energy ratios in the period between 20 and 200 ms will be discussed.

o Perhaps in no other building type is noise control as critical as in music education facilities. Of obvious importance are the room acoustics considerations of spaces for music teaching, music performance, and rehearsal. Often, however, this limited aspect of the overall environment receives an inordinate amount of attention, to the exclusion of less glamorous features. Sound isolation between critical spaces and airhandling system noise control are often the determinants of the ultimate success and even the usability of the music teaching spaces.