This paper investigates the effects of two important speech quality factors, intelligibility and loudness, on the speech quality in a wireless personal telecommunication system (referred to as PHS: the personal handy-phone system). First, using a reference system for simulating near worst-case quality conditions in the PHS, the effects of fading frequency and electric field intensity on the speech intelligibility are measured. Next, an apparatus for measuring loudness characteristics of PHS terminals is developed and using this apparatus the effects of ambient noise and the distance between a speaker's mouth and the transmitter on optimal loudness are measured and a method is presented for determining the optimal loudness rating (LR) in the PHS terminals.
Bibliographic reference. Nagabuchi, Hiromi / Takahashi, Akira / Ogawa, Mineyoshi (1995): "Speech intelligibility and loudness assessment in a wireless personal communication", In EUROSPEECH-1995, 1441-1444.