Section 8 - Using Facilitator Auditory Masking

The speech-range masking on the Facilitator may be used in one of two ways: voice-activated masking or continuous auditory masking. When masking is found to be facilitative in improving either speech or voice, the Facilitator will be most useful worn out of the clinic as a portable, assistive device.

It was established early in the literature (Hanley and Steer, 1949) that talking against increasing noise can alter the speaker’s rate of speech and change quality and intensity of voice.

The use of auditory masking to produce a reflexive vocal response was introduced in 1911 by Lombard. Known as the Lombard effect, masking is typically used today for identifying some hearing function in patients whose hearing loss is suspected to be possible malingering. The original use of Lombard masking, however, was to uncover phonation in patients with functional aphonia. As cited in Section 4 of this Manual, we use masking today to establish voice in patients with aphonia and often to uncover better vocal function in patients with functional dysphonia. Culton and Casper (1995) describe "energizing the voice" in voice therapy; for some patients with weak voices, masking often seems to "energize" the voice. For the patient who seems to have normal speech-voice physical structures, but who experiences a feeble speech-voice pattern, masking will often uncover a better, louder voice when the patient cannot monitor what is being said because of masking interference.

Masking has also been used to facilitate clearer speech/louder voice in some patients with dysarthria, decrease the negative influence of oral apraxia in some nonfluent aphasic patients, and increase fluency in some stutterers. In studio work with professional users of voice (announcers, actors, singers), masking conditions often produce better speech and voice. Once the improved speech-voice is uncovered through masking, the better response is recorded and used as a target goal in training. Winkworth and Davis (1997) found that although masking for normal subjects causes increases in vocal loudness, these loudness changes are produced by individualized changes in breathing patterns for each subject.

While most masking used in therapy is provided by either white noise or pink noise, the masking on the Facilitator is speech-range masking, focused in a bandwidth from 100–8000 Hz. The advantage of speech-range masking is that it permits the masking noise to be effective at much lower loudness levels than when using white or pink noise. Effective masking in speech or voice therapy is that level of loudness that interferes with the patient’s auditory self-monitoring system. One must ask the question, "What do patients end up sounding like when they cannot hear themselves speak or voice?" For those patients who sound better under auditory masking, it may be that their regular ongoing auditory feedback is somehow defective; i.e., the patients speak better without the real-time auditory feedback that most normal subjects appear to require.

In both diagnostic and therapy settings, the use of auditory masking may be used to differentiate whether or not such noise interference facilitates improved patient response.

Examples of Cases Using Masking

Matthew was a seven-year-old boy who had a history of bilateral vocal nodules, previously treated successfully with voice therapy (no further nodules, normal voice). Five months after therapy, however, Matthew had a severe cold with laryngitis which left him with no voice at all. This aphonia continued for six weeks before he was seen in a university clinic. Speech-range masking was used diagnostically after attempts at modeling and request for voice failed. He was asked to read aloud and speech-range masking was introduced at about 80 dB; as the masking came on, a fragile, light voice was heard instantly and was recorded on a cassette. Continued application of masking at slightly higher intensity levels resulted in a stronger, normal voice. He was then asked to hear the recording of his newly found voice. After a few voice attempts without masking, he was able to match his rediscovered voice on the recording by producing his own normal voice. A few voice therapy sessions with his school SLP seemed to establish his return of a normal voice. He has had a normal voice now for more than a four-year period.

Scott, age 29, took speech-voice improvement lessons in a New York City voice studio. Upon moving to the large NYC market, he was told by a local radio station to seek help to improve the quality of his speaking voice. As part of his studio evaluation, several areas were identified that needed work if he were to improve his voice: one, he needed to improve his breath support; two, he needed to improve his posture and overall body-carriage; and three, he needed to improve the "timbre" of his voice. He subsequently had good progress in improving both the respiratory and postural aspects required for a good speaking voice. Yet his speaking voice remained weak. Finally, in one session, he donned headphones and a microphone, and was hooked up to an auditory masking unit. As he read a script aloud, about 80 dB of masking was introduced and there was a sudden improvement in voice quality. The voice "timbre" he had been lacking was suddenly there. When he compensated vocally for the auditory masking interference, he spoke in a louder voice with better projection qualities ( as well as speaking a bit slower). The voice he produced under conditions of masking was difficult for him to produce without masking. Subsequently, it was decided that Scott should wear a portable masking device with headphones in and out of the studio. The masking provided him with the constant feedback interference which in his case facilitated a fuller, richer voice. Eventually, he was able to produce the good studio voice on his own without the need for further masking.

Recommended Procedures for Using Masking

1. It should be decided first if continuous masking will be used or if masking will only operate when the patient is voicing. Continuous masking is achieved by turning the mode switch until the word Masking shows on the display window. If voice-activated masking is preferred, press the Adjust button which will show as Masking (voiced) in the display window. Continuous masking is usually the choice for the aphonic patient or the patient who has a very weak voice (their insufficient voice signal would not activate the mechanism); such patients require the clinician to turn on continuous masking as appropriate. Voice-activated masking is the masking choice if the patient has enough voice to activate the voice-activation mechanism. Voice-activated masking is the usual masking choice for the patient who is wearing the Facilitator as a portable, assistive device.

2. If absolute intensity SPL values need to be determined when using masking, an SPL meter should be placed on a headphone. SPL values may be taken directly at the phone level. The masking unit is designed with an approximate gain range of 26 dB with the clinician operating the VOLUME control, lowering or raising masking intensity.

3. A typical application of continuous masking would follow this procedure. After the patient puts on the headphones, ask the patient to read aloud or count to thirty. After reading or counting has been established, turn on continuous masking. Shut the masking off after several words. Then repeat the masking. Do as often as needed to establish the voicing differences under the masking condition.

4. Voice-activated masking is established by turning the mode switch to Masking (voiced). The masking will only occur when the patient is voicing. This is the typical setting for patients wearing the Facilitator as a portable device.

5. A tape recorder may be needed to record the patient’s voice with or without masking. If a good target model has been obtained under masking conditions, play back the recording and see if the patient can match it without the need for further masking.

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(1) Culton, R.H. and Casper, J.K. (1995). Understanding Voice Problems, 2nd Edition. Baltimore, MD: William & Wilkins.

(2) Hanley, T.D. and Steer, M.D. (1949). Effect of distracting noise upon speaking rate, duration, and intensity. J. of Speech and Hearing Disorders, 14: 363-368.

(3) Lombard, E. (1911). Le signe de l’elevation de la voix. Annales Maladies Oreilles Larynx Nez Pharynx, 37: 101-119

(4) Winkworth, A.L. and Davis, P.J. (1997). Speech breathing and the Lombard effect. J. of Speech, Language, and Hearing Research, 40: 159-169.

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