Speech intelligibility deterioration for normal hearing and hearing impaired patients with different types of tinnitus

•The tinnitus causes deterioration in the speech intelligibility.•Normal hearing tinnitus patients have higher SRTs than control group without tinnitus.•The highest SRTs was observed for tinnitus, located in the frequency band 1.5–5 kHz. Many tinnitus subjects report problems with communication, in particular, difficulties with the intelligibility of speech when it is presented in the background of noise. The type of tinnitus (tone-like, noise, etc.), its location and range in the frequency domain, and the type and degree of accompanying hearing loss can affect speech intelligibility in noise in different ways. The main purpose of this study was to determine the effects of tinnitus and degree of hearing loss on the intelligibility of speech when it is presented in a background noise. A group of 128 patients participated in the study. There were persons with tinnitus and sensorineural hearing loss as well persons with tinnitus without hearing loss. All participants were patients of the Laryngological Centre of Rehabilitation, Medical University in Poznań. The age of patients ranged from 31 to 84 years. An additional group of 10 subjects (24–50 years) with normal hearing and without tinnitus took part in this study as a control group. An initial experiment was concerned with the determination of the tinnitus type. A band of noise of different widths (Q-factor, goodness), with varying centre frequency (f) was used to match the perceived tinnitus type. The Q factor is the ratio of the centre frequency to the noise bandwidth. In the main experiment, the Speech Reception Threshold (SRT) was measured using The Polish Sentence Test (PST). In this test, short sentences were presented in a background of a so-called babble-noise reflecting the averaged spectrum of Polish speech. among the different types of signal used by patients to match their tinnitus, the ones most often used were broadband noise in the medium frequency range (BM) and tone-like high-frequency noise (TH). The average Speech Reception Threshold (SRT) for tinnitus patients with normal hearing was 3 dB higher than that for the control group. The highest deterioration in speech intelligibility was observed for broadband tinnitus, located in the mid-frequency band (1.5–5 kHz). Tinnitus patients with normal hearing threshold have significantly higher speech reception thresholds (SRT, on average by 3 dB) than normally hearing subjects (control group, without tinnitus), when the speech is presented in a b