Interview with Richard Seewald Ph.D., Audiologist, Creator of 'DSL'
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AO/Beck: Hi Rich, it is an honor to speak with you.
Seewald: Thanks Doug. It's nice to spend time with you too.
AO/Beck: Rich, before we get to DSL and related pediatric and fitting issues, let's talk a little about your background, if that's OK?
Seewald: Sure Doug.
AO/Beck: Please tell me a little about your education.
Seewald: I received my master's degree in 1972 from the University of Minnesota and I practiced at the Nova Scotia Speech and Hearing Clinic until 1976.
AO/Beck: When did you get your Ph.D.?
Seewald: I got my Ph.D. at the University of Connecticut at Storrs in 1981. Mark Ross was my supervisor. My dissertation was on speech perception and speech production in children with hearing loss.
AO/Beck: What a great time to be at Storrs! Dr. Ross is obviously one of the shining jewels of our profession, and at that time there was a ton of speech perception work going on. It must've been an exciting time for you.
Seewald: It was indeed. I was in the right place at the right time. I feel very fortunate to have been part of it.
AO/Beck: And then from Storrs, where did you go?
Seewald: I went to teach at Ithaca College in New York for two years and then I went to Dalhousie University in Halifax, Nova Scotia and I was there from 1982 to 1986. Since then I've been here at the University of Western Ontario. Currently I am a professor at the National Center for Audiology in the School of Communication Sciences and Disorders.
AO/Beck: Does your center offer graduate studies in audiology?
Seewald: Yes. We have graduate studies in both Audiology and Speech-Language Pathology. Elizabeth Skarakis-Doyle is the Acting Chairperson of the program. We take 15 audiology graduate students per year. Currently we have a Ph.D. program and we are seriously investigating the possibility of offering an Au.D. program.
AO/Beck: Rich, can you please tell me, how many audiology programs are in Canada?
Seewald: In all of Canada, there are only 4 audiology programs. We're the largest.
AO/Beck: Very good. Please tell me the names and the titles of the faculty at your facility.
Seewald: Sure Doug. At the present time we have five full-time academic faculty in the audiology program and they include: Donald Jamieson, Ph.D. - Don works in the areas of spoken-language communication, hearing science and computer applications in speech perception and speech production training. Margaret Cheesman, Ph.D. - Meg's primary interests include aging and hearing and hearing conservation. Prudence Allen, Ph.D. - Prudy works primarily in the area of developmental psychoacoustics and central auditory processing in children. Theodore Venema, Ph.D. - Ted teaches in the areas of amplification, diagnostic audiology and hearing science. We also have two full-time Clinical Faculty in our program including Shane Moodie, M.Cl.Sc. and Frances Richert, M.Sc. With the development of our new National Centre for Audiology, we project the addition of five new positions to the existing faculty compliment.
AO/Beck: OK, let's discuss the Desired Sensation Level (DSL) fitting method. Why and when did you develop DSL?
Seewald: DSL came out of my work as a clinician in Halifax in the 1970s. I recognized there was no systematic protocol for selecting and fitting hearing aids specific to young children. In 1972, we had a major Rubella epidemic in the maritime provinces of Canada. As a result, we had lots of infants with hearing loss and we had to diagnose and fit them. As I looked around, I couldn't find much to help. So around 1975 or so, I read a chapter by Mark Ross that was all about fitting hearing aids to pre-verbal children. I decided to study under Mark and see what we could figure out. Mark and I collaborated in the late 1970s. He had developed a really interesting protocol, but the down side was that it took about 45 minutes to do the calculations by hand to determine the desired amplification characteristics for each child. Fortunately, computers were just starting to emerge, and so I thought maybe I could put together a program that would give a high quality, individualized fitting, using a computer to minimize the time and maximize the result. Here I am more than 20 years later, still working on this interesting clinical problem!
AO/Beck: What revision of DSL are you on at this point?
Seewald: We've had version 4.1 out since 1997, and we are just starting to work on version 5.
AO/Beck: What will version 5 have, that 4.1 doesn't have?
Seewald: Well, as you know Doug, as a result of infant hearing screening programs there is now a lot of interest in pediatric fitting. We know more about this now than we did when we developed version 4.1. So, version 5 will contain a number of enhancements and new functions that specifically relate to hearing aid fitting in infants. In addition, we plan to overhaul the user interface and improve our graphic presentations.
AO/Beck: What are the programs that are competitive with the DSL program?
Seewald: The only other generic evidence-based procedure which I am aware of is the new NAL-NL1 software system. Your readers might be interested to know that we are now engaged in some very interesting collaborative work with the NAL group.
AO/Beck: Is DSL appropriate for adults?
Seewald: DSL has been developed primarily for fitting infants and children. However, we are aware of many centers that also use DSL in their adult fittings. There is some controversy about whether or not the electroacoustic requirements for young children and adults are the same. For example, there is evidence to suggest that, on average, the preferred listening levels (PLLs) of children and newly fitted adults are not the same. We have some work in progress which should shed some new light on this issue.
AO/Beck: How do you determine PLLs for infants and young children?
Seewald: Unfortunately, there is no way that I know of to directly measure PLL information in pre-verbal children. However, we have studied the PLLs in older children with hearing loss, and we extrapolate those data to younger children and infants. Of course, we do know that the 2cc coupler requirements for a given hearing loss will differ between infants and older children because of the variation in real-ear to coupler difference (RECD) values as a function of age. In collaboration with the group at the Boys Town National Research Hospital we have collected a large data set on RECDs as a function of age. New predictive equations derived from these data will be incorporated into version 5 of the DSL software system.
AO/Beck: What about using speech audiometry in the DSL program?
Seewald: DSL does not recommend any particular measure for testing speech perception. There are two reasons for this. First, we have always tried to maintain an international prespective in developing the method - obviously the speech testing materials that one would use in Kansas would be different from those used in Copenhagen or in Buenos Aires. However, the main difficulty we have is in performing speech perception testing in the population that is of primary interest to us. Perhaps it is different elsewhere but we see very few Canadian babies who have much interest in repeating lists of monosyllabic words! For these reasons, we prefer to use predictive electroacoustic measures. We now have an extensive series of studies underway that will help us improve our predictions of real-speech hearing aid output from clinical electroacoustic measures.
AO/Beck: How many people use DSL across the world?
Seewald: We have at least 900 copies of the stand alone software out there. Of course, that does not include the hearing aid manufacturers who have licensed it and make it available through their hearing aid fitting software. So there are probably thousands using it. Just about all of the major manufacturers have DSL available on their software fitting systems.
AO/Beck: Can you please give me the website address and the contact information for people who might like to get the demo version of DSL, and for those who might like to follow-up directly with you?
Seewald: Sure Doug. The readers can go to www.dslio.com.
AO/Beck: Very good. Rich, again, I want to thank you for your time and I wish you continued success with DSL.
Seewald: Thanks Doug, it's been a lot of fun. I enjoy reading Audiology Online and I thank you for this opportunity.
Seewald: Thanks Doug. It's nice to spend time with you too.
AO/Beck: Rich, before we get to DSL and related pediatric and fitting issues, let's talk a little about your background, if that's OK?
Seewald: Sure Doug.
AO/Beck: Please tell me a little about your education.
Seewald: I received my master's degree in 1972 from the University of Minnesota and I practiced at the Nova Scotia Speech and Hearing Clinic until 1976.
AO/Beck: When did you get your Ph.D.?
Seewald: I got my Ph.D. at the University of Connecticut at Storrs in 1981. Mark Ross was my supervisor. My dissertation was on speech perception and speech production in children with hearing loss.
AO/Beck: What a great time to be at Storrs! Dr. Ross is obviously one of the shining jewels of our profession, and at that time there was a ton of speech perception work going on. It must've been an exciting time for you.
Seewald: It was indeed. I was in the right place at the right time. I feel very fortunate to have been part of it.
AO/Beck: And then from Storrs, where did you go?
Seewald: I went to teach at Ithaca College in New York for two years and then I went to Dalhousie University in Halifax, Nova Scotia and I was there from 1982 to 1986. Since then I've been here at the University of Western Ontario. Currently I am a professor at the National Center for Audiology in the School of Communication Sciences and Disorders.
AO/Beck: Does your center offer graduate studies in audiology?
Seewald: Yes. We have graduate studies in both Audiology and Speech-Language Pathology. Elizabeth Skarakis-Doyle is the Acting Chairperson of the program. We take 15 audiology graduate students per year. Currently we have a Ph.D. program and we are seriously investigating the possibility of offering an Au.D. program.
AO/Beck: Rich, can you please tell me, how many audiology programs are in Canada?
Seewald: In all of Canada, there are only 4 audiology programs. We're the largest.
AO/Beck: Very good. Please tell me the names and the titles of the faculty at your facility.
Seewald: Sure Doug. At the present time we have five full-time academic faculty in the audiology program and they include: Donald Jamieson, Ph.D. - Don works in the areas of spoken-language communication, hearing science and computer applications in speech perception and speech production training. Margaret Cheesman, Ph.D. - Meg's primary interests include aging and hearing and hearing conservation. Prudence Allen, Ph.D. - Prudy works primarily in the area of developmental psychoacoustics and central auditory processing in children. Theodore Venema, Ph.D. - Ted teaches in the areas of amplification, diagnostic audiology and hearing science. We also have two full-time Clinical Faculty in our program including Shane Moodie, M.Cl.Sc. and Frances Richert, M.Sc. With the development of our new National Centre for Audiology, we project the addition of five new positions to the existing faculty compliment.
AO/Beck: OK, let's discuss the Desired Sensation Level (DSL) fitting method. Why and when did you develop DSL?
Seewald: DSL came out of my work as a clinician in Halifax in the 1970s. I recognized there was no systematic protocol for selecting and fitting hearing aids specific to young children. In 1972, we had a major Rubella epidemic in the maritime provinces of Canada. As a result, we had lots of infants with hearing loss and we had to diagnose and fit them. As I looked around, I couldn't find much to help. So around 1975 or so, I read a chapter by Mark Ross that was all about fitting hearing aids to pre-verbal children. I decided to study under Mark and see what we could figure out. Mark and I collaborated in the late 1970s. He had developed a really interesting protocol, but the down side was that it took about 45 minutes to do the calculations by hand to determine the desired amplification characteristics for each child. Fortunately, computers were just starting to emerge, and so I thought maybe I could put together a program that would give a high quality, individualized fitting, using a computer to minimize the time and maximize the result. Here I am more than 20 years later, still working on this interesting clinical problem!
AO/Beck: What revision of DSL are you on at this point?
Seewald: We've had version 4.1 out since 1997, and we are just starting to work on version 5.
AO/Beck: What will version 5 have, that 4.1 doesn't have?
Seewald: Well, as you know Doug, as a result of infant hearing screening programs there is now a lot of interest in pediatric fitting. We know more about this now than we did when we developed version 4.1. So, version 5 will contain a number of enhancements and new functions that specifically relate to hearing aid fitting in infants. In addition, we plan to overhaul the user interface and improve our graphic presentations.
AO/Beck: What are the programs that are competitive with the DSL program?
Seewald: The only other generic evidence-based procedure which I am aware of is the new NAL-NL1 software system. Your readers might be interested to know that we are now engaged in some very interesting collaborative work with the NAL group.
AO/Beck: Is DSL appropriate for adults?
Seewald: DSL has been developed primarily for fitting infants and children. However, we are aware of many centers that also use DSL in their adult fittings. There is some controversy about whether or not the electroacoustic requirements for young children and adults are the same. For example, there is evidence to suggest that, on average, the preferred listening levels (PLLs) of children and newly fitted adults are not the same. We have some work in progress which should shed some new light on this issue.
AO/Beck: How do you determine PLLs for infants and young children?
Seewald: Unfortunately, there is no way that I know of to directly measure PLL information in pre-verbal children. However, we have studied the PLLs in older children with hearing loss, and we extrapolate those data to younger children and infants. Of course, we do know that the 2cc coupler requirements for a given hearing loss will differ between infants and older children because of the variation in real-ear to coupler difference (RECD) values as a function of age. In collaboration with the group at the Boys Town National Research Hospital we have collected a large data set on RECDs as a function of age. New predictive equations derived from these data will be incorporated into version 5 of the DSL software system.
AO/Beck: What about using speech audiometry in the DSL program?
Seewald: DSL does not recommend any particular measure for testing speech perception. There are two reasons for this. First, we have always tried to maintain an international prespective in developing the method - obviously the speech testing materials that one would use in Kansas would be different from those used in Copenhagen or in Buenos Aires. However, the main difficulty we have is in performing speech perception testing in the population that is of primary interest to us. Perhaps it is different elsewhere but we see very few Canadian babies who have much interest in repeating lists of monosyllabic words! For these reasons, we prefer to use predictive electroacoustic measures. We now have an extensive series of studies underway that will help us improve our predictions of real-speech hearing aid output from clinical electroacoustic measures.
AO/Beck: How many people use DSL across the world?
Seewald: We have at least 900 copies of the stand alone software out there. Of course, that does not include the hearing aid manufacturers who have licensed it and make it available through their hearing aid fitting software. So there are probably thousands using it. Just about all of the major manufacturers have DSL available on their software fitting systems.
AO/Beck: Can you please give me the website address and the contact information for people who might like to get the demo version of DSL, and for those who might like to follow-up directly with you?
Seewald: Sure Doug. The readers can go to www.dslio.com.
AO/Beck: Very good. Rich, again, I want to thank you for your time and I wish you continued success with DSL.
Seewald: Thanks Doug, it's been a lot of fun. I enjoy reading Audiology Online and I thank you for this opportunity.
