Vocal Intelligibility
(Speech Recognition)

The NlightN overcomes another deficiency of the conventional speaker because of its extraordinarily wide bandwidth. Conventional speakers have separate horns for the high and the midrange frequencies with a crossover point in the middle of the vocal range. Since the NlightN has no crossover, the vocals are as clear and crisp as the recording being reproduced.

The dispersion characteristics from each satellite cover a 180 degree arc across all frequencies so that there is no change in clarity, irrespective of the listening angle. In addition the sound pressure level is better maintained over distance, so listeners close to the speakers are not deafened while those several meters from the speakers still benefit from sound reinforcement. The net effect is that intelligibility levels have been significantly improved.

Links

A World of Reflections

Sound Power

Technical Articles

Improvements in Intelligibility Through the Use of Diffuse Acoustic Radiators in Sound Distribution (Pre-Print #4634)

Peter Mapp and Martin Colloms

Abstract

The unique sound generation and radiation characteristics of distributed mode panel loudspeakers are shown to produce improved intelligibility under given listening conditions. The improvement mechanisms are investigated and shown to be related to a number of unique features of this type of radiator including transient response, synergetic decay, low inherent distortion, directivity, and the diffuse nature of acoustic radiation.

Presented at the 103rd Conference, Audio Engineering Society, 1997 September 26-29, New York

The study report can be downloaded from the internet ($10) at the AES website. Search by Pre-Print number or author name. http://www.aes.org/publications/preprints/search.html

Sound Power – The Forgotten Loudspeaker Parameter (No Pre-Print. See below.)

Peter Mapp (Peter Mapp Associates, Colchester, Essex, C03 4JZ, UK)

Abstract

The Sound Power radiation characteristic of a loudspeaker is shown to be an essential but forgotten parameter in sound system design and loudspeaker characterisation. A study has been made of the Sound Power radiation characteristics of a wide range of devices including the new class of device the Distributed Mode Loudspeaker. Data is presented which suggests that in most commercial / industrial and professional applications, it is the sound power response that dominates the situation. The parameter is shown to directly relate to speech intelligibility and it is concluded that this useful parameter should be included in manufacturers data sheets & information.

Presented at the 110th Convention, Audio Engineering Society, 2001 May 12-15, Amsterdam, The Netherlands

The study report can be downloaded from the internet ($10) at the AES website. Search by Pre-Print number or author name. http://www.aes.org/publications/preprints/search.html

Sound Power – The Forgotten Loudspeaker Parameter

Peter Mapp, Peter Mapp Associates

With most loudspeakers, the sound pressure spectrum (frequency response) and sound power spectrum are substantially different. It is sound power that drives the reverberant response of a room, leading to a poor experience for the majority of listeners who were seated off-axis, where the direct sound was also not flat. This mismatch leads to diminished speech intelligibility and reduced musical enjoyment. The more similar spectra from distributed mode loudspeakers and other constant directivity devices may be one reason why they perform unexpectedly well in some installations.

http://www.ioa.org.uk/

Effect of Loudspeaker Type on the Identification of Vowel-like Harmonic Complexes (Pre-Print #5456)

S. Flanagan (AES Member), B.C.J. Moore (AES Member), University of Cambridge, Experimental Psychology, Downing Street, Cambridge, CB2 3EB, UK

Abstract

We investigated how the identification of vowel-like harmonic complex tones (35 harmonics of a 100-Hz fundamental) is affected by reproduction using either a conventional two-way cone loudspeaker or a distributed mode loudspeaker (DML) in a typical listening room. The harmonics were equal in amplitude except for three pairs of successive harmonics located at the first, second, and third formant frequencies of each of six possible vowels; these harmonics were incremented in level (spectral contrast). Subjects identified which vowel, chosen at random, was presented on each trial. The object was to determine whether the different sound fields created by the cone loudspeaker and the DML have an influence on the spectral contrast needed for vowel identification. The experiment is in progress.

Presented at the 111th Convention, Audio Engineering Society, 2001 September 21-24 New York

The study report can be downloaded from the internet ($10) at the AES website. Search by Pre-Print number or author name. http://www.aes.org/publications/preprints/search.html

Eton College Introduces NXT Public Address System (NXT Press Release)

The high stone walls and fan-vaulted roof of the 15th century Eton College Chapel provided an excellent acoustic environment for choral and organ music, but they made the amplified spoken word practically unintelligible. However, that problem has now been successfully addressed by a new computer-controlled speech reinforcement system using NXT flat-panel loudspeakers.

http://www.nxtsound.com/industries/articles.php?p_year=2001&MODE=NEWS#

Privacy with Intelligibility: A Novel Electroacoustic Solution

Peter Mapp, Peter Mapp Associates

Abstract

Whereas locating loudspeakers in the ceiling void or within a plenum assists sound diffusion and evenness of coverage, this also degrades speech intelligibility and causes significant non linear (frequency dependent) transmission losses. Conversely, installing conventional loudspeakers directly into the ceiling can result in good intelligibility, but poor sound diffusion, leading to uneven sound distribution and immediate localisation of the loudspeaker as the sound source. The, diffuse, substantially decorrelated and wide dispersion characteristics of the Distributed Mode Loudspeaker suggests that systems employing this new class of device may simultaneously satisfy the acoustic requirements for both speech privacy and speech intelligibility.

Presented at the 140th Meeting of the Acoustical Society of America, 2000 December, Newport Beach. http://asa.aip.org/

This study report can be downloaded from the Internet (free) from the NXT Sound website at http://www.nxtsound.com/technology/techPapers.php#

Development of an Accurate, Handheld, Simple-to-Use Meter for the Prediction of Speech Intelligibility

Herman J M Steeneken and Jan Verhave, TNO Human Factors, The Netherlands, Steve McManus, Gold Line Corporation and Ken Jacob, Bose Professional Systems

Ken Jacob described the development of a handheld meter for the accurate measurement of intelligibility. The various codes and standards now require sound systems for emergency purposes to meet or exceed a minimum level of speech intelligibility. Measuring compliance with standards normally requires complex instrumentation and expert technicians. The handheld meter described in this paper was developed to make measurements of speech intelligibility easy to do for both experts and non-experts alike.

http://www.ioa.org.uk/

The NXT Technical Review 01, January 2002

Available for internet download at: http://www.nxtsound.com/technology/techReview.php