Speech perception in quiet and noise using the hearing in noise test and the Japanese hearing in noise test by Japanese listeners.

OBJECTIVE: The aim of this study was to evaluate the first-language (L1) and second-language (L2) perception abilities in quiet and noise of native Japanese listeners who acquired English late in life and lived in the United States. The study addressed two primary questions: (1) whether native Japanese listeners who developed some fluency in English showed poorer English speech perception ability in quiet and noise than native English listeners, and (2) whether native Japanese listeners living in an English-speaking environment demonstrated poorer speech perception ability in Japanese than native Japanese listeners who reside in Japan and rarely use a second language.
DESIGN: Ten native Japanese adults who had excellent English word recognition ability in quiet were evaluated using the English and Japanese versions of the Hearing in Noise Test (HINT). In addition, 10 native English adults were evaluated using the English version of the HINT. All Japanese participants started learning English between the ages of 12 and 13 yrs while at school in Japan and had lived in the United States more than 4 yrs. An adaptive procedure was used to measure English and Japanese speech recognition thresholds (SRTs) in quiet and signal-to-noise ratios (SNRs) at which SRTs were obtained in noise conditions. In addition, a fixed-level procedure was used to obtain percent correct recognition scores at five different SNRs. Both HINT sentence stimuli and noise were presented at a simulated 0° azimuth under headphones.
RESULTS: The Japanese group had significantly poorer English speech perception ability than the native English group in all the test conditions under both the adaptive and fixed-level procedures. The psychometric function for the Japanese listeners was shifted by approximately 3 to 4 dB SNR from that of the native English listeners. Japanese speech recognition ability by the Japanese group was not significantly different from that of native Japanese speakers who live in Japan.
CONCLUSION: The Japanese participants who had excellent English word recognition ability in quiet listening conditions failed to reach native-like English speech perception when presented with sentences in quiet conditions. In addition, all 10 Japanese listeners examined in this study had HINT SNRs (i.e., SNRs at which SRTs were obtained in noise conditions) outside the normal range. However, the possible deterioration of L1 speech perception after living in the L2 environment for an extended period of time was not observed among the Japanese, late L2 learners in this study. The implication of this study for clinical settings is that it is important to use L1 sentence materials in both quiet and noise to examine the speech recognition performance of L2 (English) users who had acquired L2 after puberty.