This is a pictograph of an adult person holding an ideograph for voice. The combined glyph is an ideograph for a town crier.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-99 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 37: Collections in India: Suomalainen Tiedeakatemia.
Image credit:
Indus Script Sign Number 30: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.