Effect of Type of Speech Equalization and Averaging Method on the Long-Term Average Speech Spectra of Five Indian Languages and British English

The purpose of this study was to compare two methods for determining the long-term average speech spectrum (LTASS) across languages-root-mean-square equalization and averaging (RMSe) and loudness equalization and averaging (Le)-and to assess their implications for hearing aid fitting methods.

Audiologists fitting hearing aids for speakers of Indian languages should be cautious about applying British English or generic LTASS targets, as equalization and averaging method choices meaningfully affect the speech spectrum profile; language-specific LTASS data from this study may support more accurate prescriptive fitting for these populations.

Most hearing aid fitting protocols rely on speech spectra derived from English or a small set of Western languages; establishing validated LTASS norms for Indian languages addresses a significant gap for the world's largest hearing-impaired population in South Asia.

1. 01Long-term average speech spectra (LTASS) were measured for five Indian languages and British English.
2. 02RMS equalization and different averaging methods were systematically compared.
3. 03Results showed method-dependent differences in LTASS that have implications for hearing aid fitting accuracy.
4. 04Current hearing aid fitting targets may not adequately represent Indian language speech spectra.
5. 05Published in Journal of Speech, Language, and Hearing Research (DOI: 10.1044/2026_JSLHR-25-00909).

PMID

42234493

DOI

10.1044/2026_JSLHR-25-00909.

Journal

Journal of Speech, Language, and Hearing Research

Publication type

research_article

Evidence level

2b

Population

Speech samples from adult native speakers of five Indian languages and British English

Intervention

RMS equalization and multiple averaging methods applied to speech recordings across languages

Comparator

British English LTASS; comparison across equalization and averaging method types