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Anechoic Vocal Efforts

This page lists various anechoic vocal efforts. Please see Typical STI Applications for how they might be used when evaluating STI.

ISO 3382-3

The open plan office measurement standard defines a normal effort unisex speech spectrum. Unlike the other spectra on this page, this spectrum is for use with an omnidirectional source.

125 250 500 1000 2000 4000 8000
ISO 3382-1 Effort (1 m) 49.9 54.3 58.0 52.0 44.8 38.8 33.5

Cushing et al.

The publication by Cushing et al. 1 presents five speech efforts (hushed, normal, raised, loud and shout) for both male and female talkers, derived from 50 British English speakers. Their data closely matches the results of the well-known study by Pearsons et al. 2. A description of the vocal efforts is re-printed in the table below.

Vocal Effort Description
Hushed This is the quietest level of voiced speech – just louder than whispering. Typically this speech level would be used in intimate situations where privacy is an issue; for example talking in a library so as not to disturb others, or talking in a doctor’s waiting room.
Normal This is a normal, everyday conversational speech level. Typically this speech level would be used in small quiet room with no more than two or three people involved in the conversation.
Raised This speech level would typically be used when addressing multiple people in a medium sized room, or when in the presence of background noise such as a car or train.
Loud This speech level would typically be used when issuing commands or attracting attention, expressing anger or assertiveness. For example, when addressing a large number of people in a very large room without the aid of amplification.
Shout This is the loudest possible speech level one can manage, without straining or hurting the vocal cords.

Note

The speech efforts by Cushing et al. 1 were published in 1/3 octave bands from 125 Hz to 8 kHz and were converted to single octave bands for use in IRIS. The two most distant 1/3 octave bands (100 Hz and 10 kHz) were missing, and were assumed a value of -6 dB of the adjacent 1/3 octave band. The single octave band values are presented in the table below.

Speech Effort (1 m) 125 250 500 1000 2000 4000 8000
Male Hushed 44.2 45.8 42.8 36.5 34.0 34.3 28.8
Male Normal 50.5 57.1 57.5 52.8 48.3 44.6 39.1
Male Raised 56.5 62.4 65.5 61.8 57.1 52.1 45.5
Male Loud 58.4 66.8 73.3 72.1 66.8 61.6 52.5
Male Shout 52.8 74.4 84.8 87.3 82.5 77.3 65.1
Female Hushed 34.1 47.3 42.8 36.6 33.1 38.3 33.0
Female Normal 42.2 53.8 53.8 52.1 46.9 42.3 38.5
Female Raised 42.2 59.8 60.3 60.3 57.0 48.8 43.0
Female Loud 49.0 62.2 66.0 67.6 64.0 57.6 47.5
Female Shout 37.2 63.3 72.3 79.1 74.0 68.4 54.5

IEC 60268-16

The STI standard 3 also lists some anechoic vocal efforts. Male and female octave band values are provided for two efforts (60 dBA and 70 dBA). The 60 dBA efforts are shown below (for 70 dBA, add 10 dB to each band). Refer to Section A.3.5 (Annex A) and Annex J of the STI standard for details.

IEC 60268-16 Effort (1 m) 125 250 500 1000 2000 4000 8000
Male (60 dBA) 62.9 62.9 59.2 53.2 47.2 41.2 35.2
Female (60 dBA) 65.3 58.1 50.9 44.2 43.3 42.0

  1. I. Cushing, F. Li, T. Cox, K. Worrall, T. Jackson, Vocal efforts in anechoic conditions, Appl. Acoust. 72 (2011) 695 -701. 

  2. K. Pearsons, R. Bennett, S. Fidell, Speech levels in various noise environments, EPA-600/1-77-025, U.S. Enviromental Protection Agency (1977). 

  3. International Standard IEC 60268-16 Ed. 4.0, Sound system equipment - Part 16: Objective rating of speech Intelligibility by speech transmission index (2011).