Effects of Age on Speech Perception Ability in Everyday Life

Han, Woojae; Kim, Jinsook; Lee, Junghak; Kim, Hyung-Jong

Original Article

Speech perception and production

Korean Journal of Audiology 2003;7(1):63-69.

Effects of Age on Speech Perception Ability in Everyday Life

Woojae Han¹, Jinsook Kim², Junghak Lee¹, Hyung-Jong Kim¹

¹Department of Otorhinolaryngology-Head & Neck Surgery, College of Medicine, Hallym University, Chunchon
²Division of Speech Pathology Audiology, College of Nature Science, Hallym University, Chunchon, Korea

연령이 일상생활에서 어음지각능력에 미치는 영향

한우재^¹^, 김진숙^²^, 이정학^¹^, 김형종^¹

^¹한림대학교 의과대학 이비인후과학교실
^²한림대학교 자연과학대학 언어청각학부

Keywords: Speech perception ability;KSPIN;SNR;Age effects.

Correspondence Author：Woojae Han, 431-070 896 Pyungchon-dong, Dongan-gu, Anyang, Korea
Tel) (031) 380-3792, Fax) (031) 380-3794, E-mail：audiologist@hallym.ac.kr

Introduction

Basically, two kinds of operations are involved in understanding of sentences. One is the reception of initial acoustic information through the auditory system, and the other is the utilization of linguistic information that is stored in memory. That is, one component in the decoding of a sentence by a listener is the extraction of a partial set of phonetic features from the acoustic signal. These phonetic features are placed in short-term memory, where they are available for further processing. The linguistic information available in the long-term memory of a listener includes knowledge of the phonological, lexical, syntactic, and semantic constraints that occur in language. A test of a listener's ability to understand everyday speech must, therefore, assess both the acoustic-phonetic and the linguistic-situation components of the process¹⁾
In 1977, the speech intelligibility in noise (SPIN) sentence materials were developed by Kalikow et al.¹⁾ The SPIN test was to assess utilization of the linguistic-situational information of speech in comparison with the utilization of acoustic-phonetic information. Its items were sentences presented in the babble-type noise, and the listener was to repeat the final word in the sentence (the key word) which was always a monosyllabic noun with an open set response. Two types of sentences were used：high-predictability (HP) items for which the key word was somewhat predictable from the context, and low-predictability (LP) items for which the final word couldn't be predicted from the context. Both types were included in ten 50-item forms of the test, which were balanced for intelligibility, key-word familiarity and predictability, phonetic content, and length. Performances of normally hearing listeners for various signal-to-noise ratios showed significantly different functions for HP and LP items.
Hutcherson performed the investigation with normal hearing subjects to determine the effects of presentation level and signal-to-babble ratio on the SPIN test in 1979.²⁾ He suggested with SPIN test results of three hearing impairments that scores may provide a more insightful estimate of discriminative ability in everyday listening situations than with conventional monosyllabic word lists. Bilger (1984) attempted that all 10 forms of SPIN test were presented to 128 listeners of age from 19 to 69 who had some degree of sensorineural hearing loss.³⁾ The 10 forms did not, however, constitute a set of equivalent forms, and there were large differences in mean performance on the low-context portions. He rerecorded the six equally different forms. This revised SPIN test is often used to assist in hearing aid selection.
Recently, "Development of a test of Korean speech intelligibility in noise (KSPIN) using sentence materials with controlled word predictability" was presented by Kim et al. in 2000.⁴⁾ The key words in the KSPIN are all were always two-syllabic nouns by taking account of various sentence forms and the questioning sentences are added to obtain the responding key words because of the different word order of Korean than English. The KSPIN also used two types of sentence：HP and LP. Both types are included in six 40-item forms. An (2002) verified the predictability and phonemic representation of key-words in the KSPIN and developed 'new test lists' by revising 67 sentences.⁵⁾ Their results, however, were based only on normalhearing listeners. Thus, it is clear that a complete evaluation of the test would involve additional work for the adequate calibration and validation with a clinical population.
One of the most significant demographic factors is the aging of the population. The geriatric population, aged 65 years or older, represented almost 7.1% of the korean population in 2000. In 2020, the over-65 population will make up 14.3%；by 2030, it will represent almost 29.8%. It will be evident of an age increase in population (Kim, 1999).⁶⁾
According to Weinstein (1994), the entire auditory system undergoes changes with age. Yanz (1984) reported that young subjects were more able than older subjects to adapt and to take advantage of an improvement in the acoustic environment.⁸⁾ Schum (1992) stuided that SPIN scores were obtained from both ears of 98 elderly hearing-impaired listeners. However, for 18% of the aged ears, the contextual cues provided in the HP sentences were not used as effectively as expected based on the normative guidelines.⁹⁾
The main purpose of this study was to investigate the difference of speech perception in noise between young and old people.

Methods

Subjects

The subjects were divided in two groups；25 young adults of normal hearing (Young-N), 20 older listeners of normal hearing (Old-N). Subjects were all residents in Korea and native speakers of Korean.
The young group was composed of 20's (male 10, female 15, the average age：26.6), whereas older group ranged from 65 to 88 of age (male 3, female 17, the average age：70.75). The puretone thresholds of all subjects were less than 30 dBHL at octave intervals from 250 through 4000 Hz. It was 17 dBHL better in Young-N than Old-N indicating discrepancy of hearing threshold according to ages.

Equipments and Conditions

All subjects were tested by GSI 33 and GSI 61 audiometers. The equipments were periodically calibrated. All tests occurred in sound booths. The conditions were +5, 0, -5 dB SNR in both 25 Young-N subjects and 20 Old-N subjects.

Procedure

Prior to administration of the KSPIN test, all subjects were tested with several routine audiometric procedures. First, tympanometry was measured to confirm the existence and nonexistence of conductive components. Only the subjects who showed A type were included. Second, puretone audiograms were recorded for both air and bone conductions 250-4000 Hz. Third, live-voice presentation of spondaic word list (Ham, 1962)¹⁰⁾ provided the estimation of speech reception thresholds at each ear. Finally, monosyllabic word list (Ham, 1962) was administered for word recognition test measuring the most comfortable level (MCL). The MCL was obtained with the regular up and down procedure. All subjects showed above 90% of word recognition score (WRS) or greater and there are no difference between groups.
The KSPIN test was administered by the speaker in the sound field. Each form of the KSPIN lists consisted of 50 sentences in compact disc recorded by a female talker who spoke the standard Korean dialect against a background speech babble by mixing 12 voices reading continuous text. The sentence and babble were separated on diffrent tape tracks, allowing free selection of SNR. The CD of KSPIN was played at SNRs of +5, 0, -5 dB with the speech track set at MCL. This MCL was estimated earlier for WRS measurement for each subject. The choice of SNR was suggested by An (2002).⁵⁾ A test of a list lasted 7-8 minutes and all tests took 50-60 minutes for each subject. The data were analyzed with .05 significant level in ANOVA (Analysis of Variance) by SPSS 10.0 software.

Results

The KSPIN scores were compared between Young-N and Old-N at the conditions of +5, 0, -5 dB SNR.
The effects of age, HP/LP and SNR were calculated based on the 3-way ANOVA (Table 1). Generally, the young group showed better performance than the old group. The scores for HP sentences were higher than for LP scores for both group. The SNR decreased, however, all scores lowered for both groups. There was no interaction among the independent variables.

Comparison of HP and LP scores

Functions relating HP and LP scores to SNR for young and older groups were shown in Fig. 1. As the SNR lowed, HP and LP scores gradually decreased in all conditions. However, both groups showed large drop at the condition of -5 dB SNR than other conditions. The data also showed the expected separation between the two functions. The HP scores appeared above the LP scores in all conditions. That is, the perception of HP context was higher than that of LP context. Both HP and LP scores for the older group were always below those for the young group.

Comparison of HP-LP differences

As shown in Table 2, HP-LP difference was not affected by age or SNR ratio statistically. With a closer observation of results, the HP-LP difference of young group was gradually increased, according to lower the SNR, 0.52 and 1.56 were recorded at the conditions of +5 and -5 dB SNR. However, older group showed the greatest difference in 0 dB SNR (1.45). In +5 dB SNR condition, correct scores of both HP and LP were similar whereas in -5 dB SNR condition, incorrect scores of both HP and LP were similar. The maximum of HP-LP difference was -5 dB SNR of young group and 0 dB SNR of old group indicating the older group couldn't utilize contextual cues in noise. This indicates that noisy situation for the older group has effect on both HP and LP. Also the older group may not use contextual clues in HP sentences as the young group does in noise. This is possibly the effect of aging.

Discussion

It was to investigate the effects of age on performance, for normally hearing subjects. As the SNR lowered, both HP and LP scores of both groups gradually decreased. This is analogous to Yanz's results (1984).⁸⁾ The HP scores appeared above the LP scores in all conditions of two groups. The expected separation between HP and LP sentences was elicited, and the perception of the HP context is higher than that of the LP context. This result also agrees with the result of SPIN showing better scores in HP sentences (Kalikow, 1977；Bilger, 1984).¹⁾³⁾ However both HP and LP scores for the older subjects were always below those for the young subjects. This difference can be ascribed either to the presumed greater hearing loss for the older as age or to a loss in cognitive abilities although they are in the normal group (Kalikow, 1977).¹⁾ Hutchinson (1989) said that the older listeners were more affected by background noise than younger listeners.¹¹⁾ Yanz (1984) elicited that the young group showed significant improvement in the accuracy of word identifications from 0 to +5 dB SNR condition, while old subjects showed no change. His results suggest that young subjects are more able than older subjects to adapt to an improvement in the acoustic environment.⁸⁾ Bergman (1976) found that poor performance on speech recognition tasks by elderly subjects may be attributed to ineffective use of contextual cues.¹²⁾ The degraded speech-in-noise function of older subjects supports the hypothesis of an auditory system dysfunction in the brainstem or auditory cortex independent of a peripheral sensitivity loss (Frisina, 1997).¹³⁾ Similar findings have been reported from studies of young and elderly subjects' performance on time-altered speech (Gordon-salant 1993).¹⁴⁾ There is a decline in response speed and in short-term memory performance with increasing age, and this decline could tend to have a negative effect on performance in a sentence-understanding task. The effect of word familiarity resulting from differences in vocabulary size would presumably tend to influence old listener's performance with spoken language. However, this result does not support the hypotheses of Hutchinson (1989) that elderly subjects were able to take about just as much advantage of contextual cues as younger adults when perceiving everyday sentences in background noise.¹¹⁾ If we have matched on puretone thresholds and WRS between two groups, age factors would have less influence on deciding the criterion in the speech perception task. Also, our young group consisted of university graduate students, whereas the older group consisted of general population, which compared with retired university faculty group (intellects) of Hutchison. The similarity of the both young and older groups in education and environment might lead to a smaller gap in the results. Also, the interval of sentences should be considered.
The speech perception in noise is influenced not only by the predictability of the words, but also by their familiarity. When a sentence is presented to a listener in a particular context, a particular word familiarity is established by earlier utterances and by the situation in which the utterance is presented. Then the comprehension of the sentence is greater than when it is presented in a more neutral context (Kalikow, 1977).¹⁾ Familiar words of young people seem to be different than those of older people. Although a number of investigators have shown the effect of word familiarity, using as a measure of familiarity the relative frequency of occurrence of a word based only on normal and young listeners. On the process of the current study, although their predictability is low, older people were corrected about 80%. Moreover, the unfamiliar words of older group showed low scores regardless of the predictability. In further study, word familiarity must be equal among lists applied to older listeners. Then, in this study, total KSPIN scores were better for list 4 than list 5 in 0 dB SNR condition. List 1 and 2, 3 and 4, 5 and 6 are paired with LP and HP sentences. After list 3 was experimented, the average score of subjects tested by list 4 was 12.65. Whereas, after list 4 was experimented, that of subjects tests by list 5 was 8.55. This indicates a possible difference between paired and unpaired list (p=0.024). The cues used early were a little remained to subjects. Therefore, for the adjustment of list, test-retest measurement of KSPIN is recommended.
Kalikow (1977) reported that some combination of HP and LP scores has the potential of predicting the ability of a hearing-impaired listener to perform in everyday communicative situations, and it may help to estimate the benefit that the individual is likely to gain from a hearing aid.¹⁾ Verschuure (1992) investigated the effect of hearing aids on speech perception in noisy situation. His results showed speech to be equally understandable with and without an aid, however, patients with steep sloping audiograms understand better and patients with a conductive hearing loss component understand less in noisy circumstances with a hearing aid.¹⁵⁾ Fetterman (2002) evaluated cochlear implant patients' ability to perform in background noise.¹⁶⁾ His results indicated that the competing noise interfered with the comprehension of the connected speech for most cochlear implant patients. Muller (2002) investigated speech understanding in noise for subjects bilaterally implanted cochlears and showed that the bilateral cochlear implantation provided more benefit than the unilateral in speech understanding in both quiet and noisy situations.¹⁷⁾ Conclusively, the KSPIN may have clinical implications in regard not only to the selection of candidates but also to the estimation of performance in different SNR situations for cochlear implantation.
It is also suggested to study whether there is any difference in response between paper-and-pencil and oral response test. Particularly, the older subject delayed response in paper-and-pencil method were observed through this study. The suggestion continues to the use of different transducers such as headphone and speaker in sound fields. The use of masking for the clinical use should also be considered. The study for relationships among the puretone average, speech reception threshold (SRT), word recognition score (WRS) and KSPIN scores regarding predictability will be interested. It is also suggested that the familiarity of the word list needs to be equivalent.

Summary and Conclusion

The main purpose of the present study was to investigate the age effects on the speech perception ability in everyday life. The KSPIN test was performed for 45 subjects with normal hearing (young group 25, old group 20).
The major results were as follows;
First, as the age increased, KSPIN scores decreased.
Second, as the SNR decreased, KSPIN scores decreased without any age effect.
Third, the scores of HP items were higher than those of LP items for both young and old adults.
Finally, the HP-LP difference in the +5, 0 dB SNR conditions was similar to both groups, but in -5 dB SNR condition, the difference of the old group was smaller than that of the young group, although it was not statistically significant.
Conclusively, the age can affect the speech perception ability in daily life. It is indicated the KSPIN can be utilized for evaluating central auditory processing disorders with further research.

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