by Monte Stern

The number of students who are deaf or hard of hearing using amplification or cochlear implants in mainstream school settings has increased dramatically. What should schools be doing to create an acoustically-adapted environment that will support each students maximum learning potential? -editor's note

In 1990, Mark Ross PhD, edited Hearing Impaired Children in the Mainstream, an expanded version of a conference on "Mainstreaming Revisited". The conference was attended by educators from all across the country who are concerned with the education of children with hearing loss. In his preface, he refers to the accounts given by former students and issues this call to the education profession: "Their challenge to us, in the interests of future generations of children, is that the advantages of the mainstream process be realized for them without the penalties of social isolation and personal unhappiness." 1

As a parent, I know all too well the nature of the challenge. In a search for answers, I have come to believe that a successful response to the challenge might lie largely in acoustics. In my attempts, as a layman, to conceptualize the benefit of appropriate acoustics, I think in terms of speech intelligibility and also in terms of hearing distance ( down to chart ). What's key to note is that when the distance between speaker and listener is doubled, sound decreases by 6 decibels (dB). Due to the need for a higher signal to noise ratio (I.e. 15+ dB with hearing loss versus 6 dB with normal hearing), the typical hearing distance of someone with hearing loss is only around 1/3 the distance for someone with normal hearing. In turn, the total listening area is on the order of 10% or so of that with normal hearing.

Dr. Carol Flexer, past president of both the Educational Audiology Association and the American Academy of Audiology, discusses the significance as follows:

"Another issue that's important concerns the concept of distance hearing and incidental learning. Hearing is a distal sense. It enables us to monitor what's happening away from our bodies. Hearing enables us

enables us to learn casually, incidentally. Hearing at a distance, overhearing, and listening into conversations at home, in the environment, in the classroom and in the community enables us to learn about our culture,. About social conditions, and human interactions. Overhearing conversations helps us gain empathy, learn about how other people do life. In fact, the literature in developmental psychology teaches us that about 90 percent of what very young children know about the world was learned incidentally, casually." 2

The two concepts of speech intelligibility and hearing distance blend together into the single concept of "Comprehension Distance" (CD). It would appear from the distance/sound relationship that All Things Equal, each 6 dB of improvement from acoustics doubles the CD radius, or the area in which our children can effectively hear and learn. Hence, in theory, and without regard to other mitigating factors, an 18 dB improvement, as in reducing classroom noise levels from 60 dBA to 42 dBA, would double the CD radius three times over (2x2x2). This results in an 8 fold increase in the final comprehension distance radius.

To visualize this, grab the type of cd that music and software ship on. The radius to the outer rim is about 8 times the radius as the tiny hole in the center. Since the area of a circle is a function of the square of the radius, an 8 fold increase in CD radius translates into a 64 fold (8x8) increase in area in which "incidental learning" can occur. That's a 6,400% difference, right?!! Skeptical? Look at a cd in your library at home. If significant gains in listening area are possible, what other accommodation can hold a candle to that in terms of increasing potential learning rates to a more level playing field???

The Social Benefits of Overhearing

Increasing CD radius may also remove the barrier of of missed social opportunities. Since students with hearing loss may not overhear their peers' planning of casual after-school get-togethers (see, increasing CD radius may also help remove the barrier of bad first impressions. Unfortunately, false stereotypes can spring forth from the common assumption that people with hearing aids can hear just as well and at the usual distances as anyone else. For example, a person who is hard of hearing can be misperceived as arrogant, indifferent, or unfriendly if he or she fails to respond (while it is simply, unbeknownst to the perceiver, because he or she didn't hear to begin with!) Or, a person with a hearing loss can be considered as being aggressive when getting just a few inches too close to the speaker in an effort to hear better. John Gottman, Ph.D., the University of Washington psychologist so famous for his groundbreaking studies on marriage and divorce, writes in his new book The Relationship Cure:

"How closely we stand or sit next to one another also sends an emotional message. if somebody steps into another person's personal space without acceptance or permission, reactions may range from slight irritation to rage. Videotaped studies have been conducted of people at parties, for example, where an experimenter purposely crowds an unwitting guest. By consistently standing just a few inches too close (according to American standards), the experimenter can back the other guest across an entire room. When guests are interviewed about their impressions after such interactions, they typically describe the experimenter as interesting, but much too aggressive." 3

Research shows that first impressions form within two minutes, become "locked in" within four, and that it can take 6-8 subsequent interactions to overcome a bad first impression.4 Since first impressions can have such a profound impact on whether a friendship starts up, no wonder so many children with hearing loss struggle with feeling accepted by their peers. According to one study "The discrepancy between the proportion of hearing-impaired and normally hearing children who expressed concern about being accepted by their peers (50% vs. 15.5%) indicates that social problems may constitute a major reflection of the effects of hearing impairment, and society's attitudes toward it, on children's development."5 Another article, based on reviews of other studies, drew this tentative conclusion: "Children with mild to moderate hearing losses may be less accepted by their peers than those with severe and profound losses. Apparently, educators need to be less concerned about acceptance of profoundly hearing-impaired children than that of hard-of-hearing children, who form the bulk of children in integrated classes."6

However, the story does not just begin with Comprehension Distance (CD) and end with unfortunate stereotyping. Did you know that noise alone can have a detrimental effect on socialization? At the Educational Audiology Association 2001 conference, Karen Anderson, a past president, reviewed the essence of a bulk of research articles published over the past 35 years from various fields. She reported the following:

  • Noise causes a person to focus attention on the most critical aspects of a situation, to the neglect of subtle interpersonal social cues.
  • A restriction of attention affects the processing of less relevant social as well as nonsocial cues.
  • Noise may cause people to oversimplify and distort perceptions of complex social relationships.

These study results are based on people with normal hearing in noisy environments. There is reason to suspect the effect may be much greater on children with hearing loss. Dr. Ross is a noted audiologist who also has the benefit of firsthand experience as a hearing aid user for over 40 years. Dr. Ross comments, "The auditory distortions produced by the hearing loss produce an equivalent of 15 dB noise in the environment. It is as if suddenly the noise in the environment has increased by 15 decibels." 7

In my humble opinion, the social ramifications of inappropriate acoustics may carry a very significant, and largely unrecognized, economic toll. While entry rates into college for students with hearing loss are close in parity with other students, the drop out rate is 71% vs. 41% for other students, and this disparity is thought to be due largely to inadequate socialization. 8 Even among intellectually gifted deaf and hard of hearing people, a longitudinal study found only 43% graduated from a four year college and a surprising 30% were unemployed. 9 Estimates of the economic burden (in 1990 dollars) of childhood hearing loss (which reportedly have been used in actual settlements) suggest a lifetime loss of income in the $300,000 to $500,000 range, along with significant additional special living and medical expenses. 10

Students with hearing loss can no longer be considered a low incidence group. We now know from very recent studies that the population of school aged children with at least mild hearing loss reaches as high as 15% of school population, and the effects of hearing loss on speech intelligibility and socialization are similar to the effects on students with more significant hearing loss. 11 The sheer size of this group vastly outnumbers the largest special education group: students with learning disabilities (who happen to also benefit from improved acoustics, along with students and teachers in general. 12 ) In the long run, the cost of appropriate acoustics must pale in comparison to the benefits. What a great opportunity we have!

Fair warning: some of the concepts discussed may be subject to qualification and debate. If you discuss the article with acousticians, you are likely to hear terms like near-field, far-field, reverberant field, Lombard effect, critical distance and reverberation radius. Acoustics is a complex field and what I have shared is based on one key principle, and, at that, is interpreted by a layman. The experts may determine the effective potential increase in Comprehension Distance resulting from improved acoustics is less, and perhaps considerably less, than the idealized numbers presented here, for a variety of reasons. Indeed, the number is apt to vary with the particular acoustical criteria selected for the classroom and with the characteristics of the individual student's hearing loss. I suspect, however, whatever the number may be, the potential social benefits may be quire significant and go a great distance to remove most, if not all, of the barriers discussed here.

In closing, for all the reasons cited above, in my opinion, appropriate acoustics should be considered an extremely high priority. While two reported due process decisions in 1994, specifically on the point of classroom acoustics, were held in favor of the parents (2 ECLPR 42 and 2 ELCPR 86), two reported sign language interpreter cases may also help further pave the way, in that they stand for the principles of access that is "as effective as" for others, and in any even at least better than 50% (, Presumably, the same principles might equally support the case for acoustics for the 95% or more of students who are hard of hearing and do not sign.

What we can know for sure is that a growing body of quantitative research, along with increasing precedents from case law, support the need for schools to provide acoustically-adapted classroom environments as an appropriate accommodation for mainstreamed deaf and hard of hearing students who depend on listening as a means of communication access. -editor's note .

Monte Stern is a Stanford-educated investor and Hands & Voices National member from Oregon . He's a staunch advocate for his teenage son, an academically gifted student who is hard of hearing. Of this article, leading professionals in the field have commented, "...I think that your article is terrific! Even if your figures may not exactly apply in all circumstances, they certainly drive home the point." -- Dr. Carol Flexer, (quoted in article). "I love the concept you described. It is definitely worth pursuing. Incidental learning (overhearing) is usually either ignored or totally underestimated." Dr. Mark Ross, University of Connecticut .

(For footnotes see bottom of page)

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Effect of Noise and Reverberation on Word Recognition:
Children with Sensorineural Hearing Loss
(from Finitzo - Hieber and Tilman, 1978)

Used with permission:

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The distance between the speaker and the hearing impaired listener is often the greatest obstacle to speech understanding. Because the intensity of a sound decreases inversely with the square of the distance to its source, the sound pressure decreases by 6 dB when the distance between the speaker and listener is doubled. Thus, if the sound pressure of a signal is 70 dB at a distance of 1/2 meter, it will be 64 dB at 1 meter, 58 dB at 2 meters and 52 dB at 4 meters. Because the ambient noise level remains constant, the SNR - and therefore speech intelligibility - worsens as the distance between the speaker and the listener increases.

Clarity of speech understanding is directly related to the distance between the speaker and the listener

Critical Distance

In a fairly quiet restaurant or classroom, the ambient noise level can be around 60 dB. A speaker with a normal voice generates a sound pressure level of 65 dB at a distance of 1 meter. If the distance between the speaker and the listener is doubled twice, to 4 meters (about 12 feet), the sound pressure level will have dropped to 53 dB, which is 7 dB less than the background noise level. In other words, the background noise totally "drowns out" the speaker's voice.



Copyright Phonak - Used with permission

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Footnotes to "Acoustics and Socialization"

1 Mark Ross, editor, (1990), Hearing-Impaired Children in the Mainstream . Parkton , Maryland : York Press, Inc., p. xii.

2 Carol Flexer, Ph.D. and Infolink videotape, Enhancing Classrooms for Listening, Language and Literacy . Alexander Graham Bell Association for the Deaf and Hard of Hearing.

3 Gottman, John M., Ph.D., and DeClaire, Joan (2001). The Relationship Cure: A 5 Step Guide for Building Better Connections with Family, Friends, and Lovers . First Edition. Crown Publishers. New York , New York . Pages 182-183.

4 Harry Mills (2000). Artful Persuasion: How to command attention, change minds, and influence people . AMACOM, American Management Association. New York , New York . Page 44.

5 Davis , J.M., Elfenbein, J., Schum, R., Bentler, R. (1986). Effects of Mild and Moderate Hearing Impairments on Language, Educational, and Psychosocial Behavior of Children. Journal of Speech and Hearing Disorders, Volume 51 , p. 61.

6 Antia, S. (1985). Children: Fact or Fiction? The Volta Review, Oct/Nov 1985 , page 285.

7 Ross, M, Ph.D., The BTE FM Video , AVR Sonovation and confirmed to this author in e-mail received by this author from Dr. Ross on 9/1/2001.

8 English, K. (1997). Self Advocacy For Students Who Are Deaf or Hard of Hearing . Austin , Texas . PRO-ED, Inc., page 4.

9 Vernon , M. and LaFalce-Landers, E. (1993). A Longitudinal Study of Intellectually Gifted Deaf and Hard of Hearing People, American Annals of the Deaf, 138(5) : 427-34.

10 Northern, J. and Downs , M (1991). Hearing in Children . Fourth Edition. Baltimore , MD. Williams & Wilkins, pages 28-29.

11 Niskar, A, Kieszak, S., Holmes, A. Esteban, E., Rubin, C. Brody, D (1998). Prevalence of Hearing Loss Among Children 6 to 19 Years of Age: The Third National Health and Nutrition Examination Survey. JAMA: The Journal of the American Medical Association, 279(14) : 1071-1075. Bess, H., Dodd-Murphy, J., Parker, R., (1998). Children with Minimal Sensorineural Hearing Loss: Prevalence, Educational Performance, and Functional Status. Ear and Hearing, 19(5) : 339-354. Boney, S.J. and Bess, F.M. (1984, November). Noise and reverberation effects in minimal bilateral sensorineural hearing loss . Paper presented to the American Speech-Language-Hearing Association, San Francisco . Crandell, C. (1993). Noise effects on children with minimal sensorineural hearing loss. Ear and Hearing, 14(3) , 210-216. E-mail received by this author from Dr. Mark Ross, 8/27/2001.

12 Seep, B., Glosemeyer, R., Hulce, E., Linn, M., Aytar, P. (2000). Classroom Acoustics, Melville , NY . Acoustical Society of America . American Speech-Language-Hearing Association. (1995, March). Position statement and guidelines for acoustics in education settings. Asha, 37 (Suppl. 14), pp. 15-19.

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