Editor's Note: This is a transcript of an AudiologyOnline live seminar. Please download supplemental course materials.
Speech is the auditory stimulus through which we communicate. The recognition of speech is therefore of great interest to all of us in the fields of speech and hearing. Speech audiometry developed originally out of the work conducted at Bell Labs in the 1920s and 1930s where they were looking into the efficiency of communication systems, and really gained momentum post World War II as returning veterans presented with hearing loss. The methods and materials for testing speech intelligibility were of interest then, and are still of interest today. It is due to this ongoing interest as seen in the questions that students ask during classes, by questions new audiologists raise as they begin their practice, and by the comments and questions we see on various audiology listservs about the most efficient and effective ways to test speech in the clinical setting, that AudiologyOnline proposed this webinar as part of their Back to Basics series. I am delighted to participate. I am presenting a review of the array of speech tests that we use in clinical evaluation with a summary of some of the old and new research that has come about to support the recommended practices. The topics that I will address today are an overview of speech threshold testing, suprathreshold speech recognition testing, the most comfortable listening level testing, uncomfortable listening level, and a brief mention of some new directions that speech testing is taking.
In the context of testing speech, I will assume that the environment in which you are testing meets the ANSI permissible noise criteria and that the audiometer transducers that are being used to perform speech testing are all calibrated to the ANSI standards for speech. I will not be talking about those standards, but it's of course important to keep those in mind.
Speech Threshold testing involves several considerations. They include the purposes of the test or the reasons for performing the test, the materials that should be used in testing, and the method or procedure for testing.
Purposes of Speech Threshold Testing
A number of purposes have been given for speech threshold testing. In the past, speech thresholds were used as a means to cross-check the validity of pure tone thresholds. This purpose lacks some validity because we have other physiologic and electrophysiologic procedures like OAEs and imittance test results to help us in that cross-check. However, the speech threshold measure is a test of hearing. It is not entirely invalid to be performed as a cross-check for pure tone hearing. I think sometimes we are anxious to get rid of things because we feel we have a better handle from other tests, but in this case, it may not be the wisest thing to toss out.
Also in past years, speech thresholds were used to determine the level for suprathreshold speech recognition testing. That also lacks validity, because the level at which suprathreshold testing is conducted depends on the reason you are doing the test itself.
It is necessary to test speech thresholds if you are going to bill 92557. Aside from that, the current purpose for speech threshold testing is in the evaluation of pediatric and difficult to test patients. Clinical practice surveys tell us that the majority of clinicians do test speech thresholds for all their patients whether it is for billing purposes or not.
It is always important that testing is done in the recommended, standardized manner. The accepted measures for speech thresholds are the Speech Recognition Threshold (SRT) and the Speech Detection Threshold (SDT). Those terms are used because they specify the material or stimulus, i.e. speech, as well as the task that the listener is required to do, which is recognition or identification in the case of the SRT, and detection or noticing of presence versus absence of the stimulus in the case of SDT. The terms also specify the criterion for performance which is threshold or generally 50%. The SDT is most commonly performed on those individuals who have been unable to complete an SRT, such as very young children. Because recognition is not required in the speech detection task, it is expected that the SDT will be about 5 to 10 dB better than the SRT, which requires recognition of the material.
Materials for Speech Threshold Testing
The materials that are used in speech threshold testing are spondees, which are familiar two-syllable words that have a fairly steep psychometric function. Cold running speech or connected discourse is an alternative for speech detection testing since recognition is not required in that task. Whatever material is used, it should be noted on the audiogram. It is important to make notations on the audiogram about the protocols and the materials we are using, although in common practice many of us are lax in doing so.
Methods for Speech Threshold Testing
The methods consideration in speech threshold testing is how we are going to do the test. This would include whether we use monitored live voice or recorded materials, and whether we familiarize the patient with the materials and the technique that we use to elicit threshold. Monitored live voice and recorded speech can both be used in SRT testing. However, recorded presentation is recommended because recorded materials standardize the test procedure. With live voice presentation, the monitoring of each syllable of each spondee, so that it peaks at 0 on the VU meter can be fairly difficult. The consistency of the presentation is lost then. Using recorded materials is recommended, but it is less important in speech threshold testing than it is in suprathreshold speech testing. As I mentioned with the materials that are used, it is important to note on the audiogram what method of presentation has been used.
As far as familiarization goes, we have known for about 50 years, since Tillman and Jerger (1959) identified familiarity as a factor in speech thresholds, that familiarization of the patient with the test words should be included as part of every test. Several clinical practice surveys suggest that familiarization is not often done with the patients. This is not a good practice because familiarization does influence thresholds and should be part of the procedure.
The last consideration under methods is regarding the technique that is going to be used. Several different techniques have been proposed for the determination of SRT. Clinical practice surveys suggest the most commonly used method is a bracketing procedure. The typical down 10 dB, up 5 dB is often used with two to four words presented at each level, and the threshold then is defined as the lowest level at which 50% or at least 50% of the words are correctly repeated. This is not the procedure that is recommended by ASHA (1988). The ASHA-recommended procedure is a descending technique where two spondees are presented at each decrement from the starting level. There are other modifications that have been proposed, but they are not widely used.
Suprathreshold speech testing involves considerations as well. They are similar to those that we mentioned for threshold tests, but they are more complicated than the threshold considerations. They include the purposes of the testing, the materials that should be used in testing, whether the test material should be delivered via monitored live voice or recorded materials, the level or levels at which the testing should be conducted, whether a full list, half list, or an abbreviated word list should be used, and whether or not the test should be given in quiet or noise.
Purposes of Suprathreshold Testing
There are several reasons to conduct suprathreshold tests. They include estimating the communicative ability of the individual at a normal conversational level; determining whether or not a more thorough diagnostic assessment is going to be conducted; hearing aid considerations, and analysis of the error patterns in speech recognition. When the purpose of testing is to estimate communicative ability at a normal conversational level, then the test should be given at a level around 50 to 60 dBHL since that is representative of a normal conversational level at a communicating distance of about 1 meter. While monosyllabic words in quiet do not give a complete picture of communicative ability in daily situations, it is a procedure that people like to use to give some broad sense of overall communicative ability. If the purpose of the testing is for diagnostic assessment, then a psychometric or performance-intensity function should be obtained. If the reason for the testing is for hearing aid considerations, then the test is often given using words or sentences and either in quiet or in a background of noise. Another purpose is the analysis of error patterns in speech recognition and in that situation, a test other than some open set monosyllabic word test would be appropriate.
Materials for Suprathreshold Testing
The choice of materials for testing depends on the purpose of the test and on the age and abilities of the patients. The issues in materials include the set and the test items themselves.
Closed set vs. Open set. The first consideration is whether a closed set or an open set is appropriate. Closed set tests limit the number of response alternatives to a fairly small set, usually between 4 and 10 depending on the procedure. The number of alternatives influences the guess rate. This is a consideration as well. The Word Intelligibility by Picture Identification or the WIPI test is a commonly used closed set test for children as it requires only the picture pointing response and it has a receptive language vocabulary that is as low as about 5 years. It is very useful in pediatric evaluations as is another closed set test, the Northwestern University Children's Perception of Speech test (NU-CHIPS).
In contrast, the open set protocol provides an unlimited number of stimulus alternatives. Therefore, open set tests are more difficult. The clinical practice surveys available suggest for routine audiometric testing that monosyllabic word lists are the most widely used materials in suprathreshold speech recognition testing for routine evaluations, but sentences in noise are gaining popularity for hearing aid purposes.
CID W-22 vs. NU-6.The most common materials for speech recognition testing are the monosyllabic words, the Central Institute of the Deaf W-22 and the Northwestern University-6 word list. These are the most common open set materials and there has been some discussion among audiologists concerning the differences between those. From a historical perspective, the CID W-22 list came from the original Harvard PAL-PB50 words and the W-22s are a group of the more familiar of those. They were developed into four 50-word lists. They are still commonly used by audiologists today. The NU-6 lists were developed later and instead of looking for phonetic balance, they considered a more phonemic balance. The articulation function for both of those using recorded materials is about the same, 4% per dB. The NU-6 tests are considered somewhat more difficult than the W-22s. Clinical surveys show that both materials are used by practicing audiologists, with usage of the NU-6 lists beginning to surpass usage of W-22s.
Nonsense materials. There are other materials that are available for suprathreshold speech testing. There are other monosyllabic word lists like the Gardner high frequency word list (Gardner, 1971) that could be useful for special applications or special populations. There are also nonsense syllabic tasks which were used in early research in communication. An advantage of the nonsense syllables is that the effects of word familiarity and lexical constraints are reduced as compared to using actual words as test materials. A few that are available are the City University of New York Nonsense Syllable test, the Nonsense Syllable test, and others.
Sentence materials. Sentence materials are gaining popularity, particularly in hearing aid applications. This is because speech that contains contextual cues and is presented in a noise background is expected to have better predictive validity than words in quiet. The two sentence procedures that are popular are the Hearing In Noise Test (HINT) (Nilsson, Soli,& Sullivan, 1994) and the QuickSIN (Killion, Niquette, Gudmundsen, Revit & Banerjee, 2004). Other sentence tests that are available that have particular applications are the Synthetic Sentence Identification test (SSI), the Speech Perception and Noise test (SPIN), and the Connected Speech test.
Monitored Live Voice vs. Recorded. As with speech threshold testing, the use of recorded materials for suprathreshold speech testing standardizes the test administration. The recorded version of the test is actually the test in my opinion. This goes back to a study in 1969 where the findings said the test is not just the written word list, but rather it is a recorded version of those words.
Inter-speaker and intra-speaker variability makes using recorded materials the method of choice in almost all cases for suprathreshold testing. Monitored live voice (MLV) is not recommended. In years gone by, recorded materials were difficult to manipulate, but the ease and flexibility that is afforded us by CDs and digital recordings makes recorded materials the only way to go for testing suprathreshold speech recognition.
Another issue to consider is the use of the carrier phrase. Since the carrier phrase is included on recordings and recorded materials are the recommended procedure, that issue is settled. However, I do know that monitored live voice is necessary in certain situations and if monitored live voice is used in testing, then the carrier phrase should precede the test word. In monitored live voice, the carrier phrase is intended to allow the test word to have its own natural inflection and its own natural power. The VU meter should peak at 0 for the carrier phrase and the test word then is delivered at its own natural or normal level for that word in the phrase.
Levels. The level at which testing is done is another consideration. The psychometric or performance-intensity function plots speech performance in percent correct on the Y-axis, as a function of the level of the speech signal on the X-axis. This is important because testing at only one level, which is fairly common, gives us insufficient information about the patient's optimal performance or what we commonly call the PB-max. It also does not allow us to know anything about any possible deterioration in performance if the level is increased. As a reminder, normal hearers show a function that reaches its maximum around 25 to 40 dB SL (re: SRT) and that is the reason why suprathreshold testing is often conducted at that level. For normals, the performance remains at that level, 100% or so, as the level increases. People with conductive hearing loss also show a similar function. Individuals with sensorineural hearing loss, however, show a performance function that reaches its maximum at generally less than 100%. They can either show performance that stays at that level as intensity increases, or they can show a curve that reaches its maximum and then decreases in performance as intensity increases. This is known as roll-over. A single level is not the best way to go as we cannot anticipate which patients may have rollover during testing, unless we test at a level higher than where the maximum score was obtained. I recognize that there are often time constraints in everyday practice, but two levels are recommended so that the performance-intensity function can be observed for an individual patient at least in an abbreviated way.
Recently, Guthrie and Mackersie (2009) published a paper that compared several different presentation levels to ascertain which level would result in maximum word recognition in individuals who had different hearing loss configurations. They looked at a number of presentation levels ranging from 10 dB above the SRT to a level at the UCL (uncomfortable listening level) -5 dB. Their results indicated that individuals with mild to moderate losses and those with more steeply sloping losses reached their best scores at a UCL -5 dB. That was also true for those patients who had moderately-severe to severe losses. The best phoneme recognition scores for their populations were achieved at a level of UCL -5 dB. As a reminder about speech recognition testing, masking is frequently needed because the test is being presented at a level above threshold, in many cases well above the threshold. Masking will always be needed for suprathreshold testing when the presentation level in the test ear is 40 dB or greater above the best bone conduction threshold in the non-test ear if supra-aural phones are used.
Full lists vs. half-lists. Another consideration is whether a full list or a half-list should be administered. Original lists were composed of 50 words and those 50 words were created for phonetic balance and for simplicity in scoring. It made it easy for the test to be scored if 50 words were administered and each word was worth 2%. Because 50-word lists take a long time, people often use half-lists or even shorter lists for the purpose of suprathreshold speech recognition testing. Let's look into this practice a little further.
An early study was done by Thornton and Raffin (1978) using the Binomial Distribution Model. They investigated the critical differences between one score and a retest score that would be necessary for those scores to be considered statistically significant. Their findings showed that with an increasing set size, variability decreased. It would seem that more items are better.
More recently Hurley and Sells (2003) conducted a study that looked at developing a test methodology that would identify those patients requiring a full 50 item suprathreshold test and allow abbreviated testing of patients who do not need a full 50 item list. They used Auditec recordings and developed 10-word and 25-word screening tests. They found that the four lists of NU-6 10-word and the 25-word screening tests were able to differentiate listeners who had impaired word recognition who needed a full 50-word list from those with unimpaired word recognition ability who only needed the 10-word or 25-word list. If abbreviated testing is important, then it would seem that this would be the protocol to follow. These screening lists are available in a recorded version and their findings were based on a recorded version. Once again, it is important to use recorded materials whether you are going to use a full list or use an abbreviated list.
Quiet vs. Noise. Another consideration in suprathreshold speech recognition testing is whether to test in quiet or in noise. The effects of sensorineural hearing loss beyond the threshold loss, such as impaired frequency resolution or impaired temporal resolution, makes speech recognition performance in quiet a poor predictor for how those individuals will perform in noise. Speech recognition in noise is being promoted by a number of experts because adding noise improves the sensitivity of the test and the validity of the test. Giving the test at several levels will provide for a better separation between people who have hearing loss and those who have normal hearing. We know that individuals with hearing loss have a lot more difficulty with speech recognition in noise than those with normal hearing, and that those with sensorineural hearing loss often require a much greater signal-to-noise ratio (SNR), 10 to 15 better, than normal hearers.
Monosyllabic words in noise have not been widely used in clinical evaluation. However there are several word lists that are available. One of them is the Words in Noise test or WIN test which presents NU-6 words in a multi-talker babble. The words are presented at several different SNRs with the babble remaining at a constant level. One of the advantages of using these kinds of tests is that they are adaptive. They can be administered in a shorter period of time and they do not run into the same problems that we see with ceiling effects and floor effects.
As I mentioned earlier, sentence tests in noise have become increasingly popular in hearing aid applications. Testing speech in noise is one way to look at amplification pre and post fitting. The Hearing in Noise Test and QuickSin, have gained popularity in those applications. The HINT was developed by Nilsson and colleagues in 1994 and later modified. It is scored as the dB to noise ratio that is necessary to get a 50% correct performance on the sentences. The sentences are the BKB (Bamford-Kowal-Bench) sentences. They are presented in sets of 10 and the listener listens and repeats the entire sentence correctly in order to get credit. In the HINT, the speech spectrum noise stays constant and the signal level is varied to obtain that 50% point. The QuickSin is a test that was developed by Killion and colleagues (2004) and uses the IEEE sentences. It has six sentences per list with five key words that are the scoring words in each sentence. All of them are presented in a multi-talker babble. The sentences get presented one at a time in 5 dB decrements from a high positive SNR down to 0 dB SNR. Again the test is scored as the 50% point in terms of dB signal-to-noise ratio. The guide proposed by Killion on the SNR is if an individual has somewhere around a 0 to 3 dB SNR it would be considered normal, 3 to 7 would be a mild SNR loss, 7 to15 dB would be a moderate SNR loss, and greater than 15 dB would be a severe SNR loss.
Scoring. Scoring is another issue in suprathreshold speech recognition testing. It is generally done on a whole word basis. However phoneme scoring is another option. If phoneme scoring is used, it is a way of increasing the set size and you have more items to score without adding to the time of the test. If whole word scoring is used, the words have to be exactly correct. In this situation, being close does not count. The word must be absolutely correct in order to be judged as being correct. Over time, different scoring categorizations have been proposed, although the percentages that are attributed to those categories vary among the different proposals.
The traditional categorizations include excellent, good, fair, poor, and very poor. These categories are defined as:
- Excellent or within normal limits = 90 - 100% on whole word scoring
- Good or slight difficulty = 78 - 88%
- Fair to moderate difficulty = 66 - 76%
- Poor or great difficulty = 54 - 64 %
- Very poor is < 52%
A very useful test routinely administered to those who are being considered for hearing aids is the level at which a listener finds listening most comfortable. The materials that are used for this are usually cold running speech or connected discourse. The listener is asked to rate the level at which listening is found to be most comfortable. Several trials are usually completed because most comfortable listening is typically a range, not a specific level or a single value. People sometimes want sounds a little louder or a little softer, so the range is a more appropriate term for this than most comfortable level. However whatever is obtained, whether it is a most comfortable level or a most comfortable range, should be recorded on the audiogram. Again, the material used should also be noted on the audiogram. As I mentioned earlier the most comfortable level (MCL) is often not the level at which a listener achieves maximum intelligibility. Using MCL in order to determine where the suprathreshold speech recognition measure will be done is not a good reason to use this test. MCL is useful, but not for determining where maximum intelligibility will be. The study I mentioned earlier showed that maximum intelligibility was reached for most people with hearing loss at a UCL -5. MCL is useful however in determining ANL or acceptable noise level.
The uncomfortable listening level (UCL) is also conducted with cold running speech. The instructions for this test can certainly influence the outcome since uncomfortable or uncomfortably loud for some individuals may not really be their UCL, but rather a preference for listening at a softer level. It is important to define for the patient what you mean by uncomfortably loud. The utility of the UCL is in providing an estimate for the dynamic range for speech which is the difference between the UCL and the SRT. In normals, this range is usually 100 dB or more, but it is reduced in ears with sensorineural hearing loss often dramatically. By doing the UCL, you can get an estimate of the individual's dynamic range for speech.
Acceptable Noise Level (ANL) is the amount of background noise that a listener is willing to accept while listening to speech (Nabelek, Tucker, & Letowski, 1991). It is a test of noise tolerance and it has been shown to be related to the successful use of hearing aids and to potential benefit with hearing aids (Nabelek, Freyaldenhoven, Tampas, & Muenchen, 2006). It uses the MCL and a measure known as BNL or background noise level. To conduct the test, a recorded speech passage is presented to the listener in the sound field for the MCL. Again note the use of recorded materials. The noise is then introduced to the listener to a level that will be the highest level that that person is able to accept or "put up with" while they are listening to and following the story in the speech passage. The ANL then becomes the difference between the MCL and the BNL. Individuals that have very low scores on the ANL are considered successful hearing aid users or good candidates for hearing aids. Those that have very high scores are considered unsuccessful users or poor hearing aid candidates.
Obviously there are number of other applications for speech in audiologic practice, not the least of which is in the assessment of auditory processing. Many seminars could be conducted on this topic alone. Another application or future direction for speech audiometry is to more realistically assess hearing aid performance in "real world" environments. This is an area where research is currently underway.
Question: Are there any more specific instructions for the UCL measurement?
Answer: Instructions are very important. We need to make it clear to a patient exactly what we expect them to do. I personally do not like things loud. If I am asked to indicate what is uncomfortably loud, I am much below what is really my UCL. I think you have to be very direct in instructing your patients in that you are not looking for a little uncomfortable, but where they just do not want to hear it or cannot take it.
Question: Can you sum up what the best methods are to test hearing aid performance? I assume this means with speech signals.
Answer: I think the use of the HINT or the QuickSin would be the most useful on a behavioral test. We have other ways of looking at performance that are not behavioral.
Question: What about dialects? In my area, some of the local dialects have clipped words during speech testing. I am not sure if I should count those as correct or incorrect.
Answer: It all depends on your situation. If a patient's production is really reflective of the dialect of that region and they are saying the word as everyone else in that area would say it, then I would say they do have the word correct. If necessary, if you are really unclear, you can always ask the patient to spell the word or write it down. This extra time can be inconvenient, but that is the best way to be sure that they have correctly identified the word.
Question: Is there a reference for the bracketing method?
Answer: The bracketing method is based on the old modified Hughson-Westlake that many people use for pure tone threshold testing. It is very similar to that traditional down 10 dB, up 5 dB. I am sure there are more references, but the Hughson-Westlake is what bracketing is based on.
Question: Once you get an SRT result, if you want to compare it to the thresholds to validate your pure tones, how do you compare it to the audiogram?
Answer: If it is a flat hearing loss, then you can compare to the 3-frequency pure tone average (PTA). If there is a high frequency loss, where audibility at perhaps 2000 Hz is greatly reduced, then it is better to use just the average of 500Hz and 1000Hz as your comparison. If it is a steeply sloping loss, then you look for agreement with the best threshold, which would probably be the 500 Hz threshold. The reverse is also true for patients who have rising configurations. Compare the SRT to the best two frequencies of the PTA, if the loss has either a steep slope or a steep rise, or the best frequency in the PTA if it is a really precipitous change in configuration.
Question: Where can I find speech lists in Russian or other languages?
Answer: Auditec has some material available in languages other than English - it would be best to contact them directly. You can also view their catalog at www.auditec.com
Carolyn Smaka: This raises a question I have. If an audiologist is not fluent in a particular language, such as Spanish, is it ok to obtain a word list or recording in that language and conduct speech testing?
Janet Schoepflin: I do not think that is a good practice. If you are not fluent in a language, you do not know all the subtleties of that language and the allophonic variations. People want to get an estimation of suprathreshold speech recognition and this would be an attempt to do that. This goes along with dialect. Whether you are using a recording, or doing your best to say these words exactly as there are supposed to be said, and your patient is fluent in a language and they say the word back to you, since you are not familiar with all the variations in the language it is possible that you will score the word incorrectly. You may think it is correct when it is actually incorrect, or you may think it is incorrect when it is correct based on the dialect or variation of that language.
Question: In school we were instructed to use the full 50-word list for any word discrimination testing at suprathreshold, but if we are pressed for time, a half word list would be okay. However, my professor warned us that we absolutely must go in order on the word list. Can you clarify this?
Answer: I'm not sure why that might have been said. I was trained in the model to use the 50-word list. This was because the phonetic balance that was proposed for those words was based on the 50 words. If you only used 25 words, you were not getting the phonetic balance. I think the more current findings from Hurley and Sells show us that it is possible to use a shorter list developed specifically for this purpose. It should be the recorded version of those words. These lists are available through Auditec.
Question: On the NU-6 list, the words 'tough' and 'puff' are next to each other. 'Tough' is often mistaken for 'puff' so then when we reads 'puff', the person looks confused. Is it okay to mix up the order on the word list?
Answer: I think in that case it is perfectly fine to move that one word down.
Question: When do you recommend conducting speech testing, before or after pure tone testing?
Answer: I have always been a person who likes to interact with my patients. My own procedure is to do an SRT first. Frequently for an SRT I do use live voice. I do not use monitored live voice for suprathreshold testing. It gives me a time to interact with the patient. People feel comfortable with speech. It is a communicative act. Then I do pure tone testing. Personally I would not do suprathreshold until I finished pure tone testing. My sequence is often SRT, pure tone, and suprathreshold. If this is not a good protocol for you based on time, then I would conduct pure tone testing, SRT, and then suprathreshold.
Question: Some of the spondee words are outdated such as inkwell and whitewash. Is it okay to substitute other words that we know are spondee words, but may not be on the list? Or if we familiarize people, does it matter?
Answer: The words that are on the list were put there for their so-called familiarity, but also because they were somewhat homogeneous and equal in intelligibility. I think inkwell, drawbridge and whitewash are outdated. If you follow a protocol where you are using a representative sample of the words and you are familiarizing, I think it is perfectly fine to eliminate those words you do not want to use. You just do not want to end up only using five or six words as it will limit the test set.
Question: At what age is it appropriate to expect a child to perform suprathreshold speech recognition testing?
Answer: If the child has a receptive language age of around 4 or 5 years, even 3 years maybe, it is possible to use the NU-CHIPS as a measure. It really does depend on language more than anything else, and the fact that the child can sit still for a period of time to do the test.
Question: Regarding masking, when you are going 40 dB above the bone conduction threshold in the non-test ear, what frequency are you looking at? Are you comparing speech presented at 40 above a pure tone average of the bone conduction threshold?
Answer: The best bone conduction threshold in the non-test ear is what really should be used.
Question: When seeing a patient in follow-up after an ENT prescribes a steroid therapy for hydrops, do you recommend using the same word list to compare their suprathreshold speech recognition?
Answer: I think it is better to use a different list, personally. Word familiarity as we said can influence even threshold and it certainly can affect suprathreshold performance. I think it is best to use a different word list.
Carolyn Smaka: Thanks to everyone for their questions. Dr. Schoepflin has provided her email address with the handout. If your question was not answered or if you have further thoughts after the presentation, please feel free to follow up directly with her via email.
Janet Schoepflin: Thank you so much. It was my pleasure and I hope everyone found the presentation worthwhile.
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