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Spectral iQ is a frequency lowering algorithm intended for use in cases of severe-to-profound, high-frequency, sloping hearing losses. This novel technique for frequency lowering is technically described as Spectral Envelope Warping (SEW) (Fitz et al., 2009). The SEW algorithm operates by monitoring high-frequency regions for spectral peaks that are responsible for the recognition of high-frequency speech sounds like /s/ and /sh/. The algorithm characterizes the high-frequency spectral shape and dynamically recreates that spectral shape inside a lower frequency target region. The source region for analysis, target region for the newly created spectral cue and gain applied to the newly generated cue are each prescribed by the Inspire® programming software.

Candidates for Spectral iQ are those patients who meet the following audiometric criteria:

• All thresholds below 1000 Hz must be 55dBHL or better

• High-frequency hearing loss slope must be greater than or equal to 25dBHL per octave

• A single threshold between 1000 Hz and 3000 Hz must be 55dBHL or worse

• All thresholds between 4000 Hz and 8000 Hz must be 55dBHL or worse

Spectral iQ will automatically activate for patients who meet these audiometric criteria. Inspire reveals two Spectral iQ controls: Spectral iQ Bandwidth and Spectral iQ Gain. There are seven options for Spectral iQ Bandwidth and 10, 1dB steps for Spectral iQ Gain. At default settings, Spectral iQ Bandwidth is set to 3 or 5 (depending on severity of loss) and Gain is set to 3dB. Each of these is described below.

The prescription of Spectral iQ is done on an individual audiometric basis; different patients will be prescribed different algorithm parameters. Figure 1 illustrates variable parameters that are affected by Spectral iQ Bandwidth adjustments. Two audiometric markers (Figure 1, panel A, shown with red arrows) are used to define upper and lower frequency boundaries inside which seven target regions (Figure 1, highlighted in yellow) are defined. Each target region corresponds to a Spectral iQ Bandwidth setting in Inspire. A target region is the range of frequencies inside which lowered cues are presented. The lowest frequency boundary possible for a target region is the corner frequency: this audiometric marker is the lowest frequency that starts the 20dB per-octave audiometric slope. In the case of audiograms that do not exceed this slope, the lowest frequency that starts the audiometric slope will be defined as the corner frequency. The highest frequency boundary possible for a target region is the 70dBHL frequency: the exact frequency for this 70dBHL threshold is determined through linear interpolation between the measured audiometric frequencies. Increasing Spectral iQ Bandwidth (i.e. increasing sensitivity) generates target regions that fall closer to the low-frequency boundary, or corner frequency; lower Bandwidth settings (i.e. lower sensitivity) generate target regions closer to the high-frequency boundary or 70dBHL frequency.

In all panels of Figure 1, a sample patient’s audiogram is shown, the source region for analysis is shown in green and the target region is shown in yellow. In panel A, Spectral iQ Bandwidth is prescribed to more aggressive parameters. The source region for analysis covers a broad range of high frequencies, while the target region falls between 500 Hz and 2000 Hz. The example in Panel A may correspond with a Spectral iQ Bandwidth setting of six or seven. In panel B a moderate setting is illustrated. The source region

The Prescription of Spectral iQ*

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for analysis remains the same and the target region has narrowed in frequency. Panel C shows an illustration of mild Spectral iQ settings. The source region for analysis has moved higher in frequency, focusing only on the highest frequency information and the target region has narrowed and shifted higher in frequency.

Spectral iQ Gain refers to gain applied to the newly generated spectral cue. This value is relative to gain prescribed across the target region. For example, if the target region spans 1000 Hz and 3000 Hz and the gain applied in that range is 20dB, a Spectral iQ gain setting of 3dB will cause Spectral iQ to generate new cues that peak at 23dB inside the target region.

The source region (Figure 1, highlighted in green) for analysis changes with different prescriptions. At less aggressive settings, the source region for analysis is constrained to only the highest frequencies; at more aggressive settings, the source region for analysis will extend into lower frequencies.

Verification and Validation of Spectral iQ

In the fitting of hearing aids, it is routine clinical practice to take a measurement of hearing aid output in a patient’s ear. This process of real-ear measurement (REM) verifies sound levels for the fitted hearing aid and allows comparison to a patient’s audiometric threshold and prescriptive targets. Because Spectral iQ dynamically captures and recreates high-frequency spectral cues in real time, the averaging of level that occurs in commercial real-ear systems makes traditional real-ear measurements an inaccurate representation of the feature. However, real-ear measurements can be used to verify the activity of Spectral iQ. By comparing measurements with Spectral iQ ON and OFF, an increase in level should be observed in the target region with Spectral iQ active. Figure 2 shows two real-ear aided responses measured using an Audioscan Verifit and a speech sample that includes a

band-pass filter centered at 6300 Hz. The green response shows Spectral iQ OFF and the magenta response shows Spectral iQ ON. This difference between 2000 and 4000 Hz clearly demonstrates the frequency lowering behavior of Spectral iQ. However, it is important to note that the measured difference between the time-averaged, real-ear curves and the proximity of the Spectral iQ

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Figure 1. An illustration of three Spectral iQ prescriptions are shown at different Bandwidth settings. The audiogram in each panel is representative of a Spectral iQ candidate. Green illustrates the source region for analysis and yellow the target region. Panels A, B, and C provide illustrations of Spectral iQ Bandwidth at Maximum, Moderate and Minimum settings, respectively.

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Figure 2. Two real-ear aided responses (dB SPL) are shown as a function of frequency (Hz). The measurement stimulus (included in the Audioscan Verifit) was a speech sample with high-frequency components band–pass filtered around a center frequency of 6300 Hz. The green response shows Spectral iQ OFF and the magenta response shows Spectral iQ ON.

response to the audiogram are not expected to correlate with benefit from the feature. The stimulus presented by Spectral iQ will be averaged over time to appear lower in level during real-ear measurement; meaning that slight differences in the measured real-ear response may represent large changes in quality and audibility for the patient.

The recommended process for validation of Spectral iQ is through the use of high-frequency speech sounds. In-office presentation of an S-test, originally described by Robinson, Baer, and Moore (2007), can be used to document a patient’s ability to detect high-frequency speech sounds. The S-test is a task of English language plural detection that scores correct detection of word-final /s/ and /z/. The University of Western Ontario Plurals Test (Glista & Scollie, 2012) is an option for a standardized, recorded test corpus. A worksheet is included at the end of this document that can be used to facilitate an in-office, live-voice S-test.

References

Fitz, K., Edwards, B., & Baskent, D. (2009). U.S. Patent Application. 20090226016. Washington, DC: U.S. Patent and Trademark Office.

Robinson, J.D., Baer, T., & Moore, B.C. (2007). Using transposition to improve consonant discrimination and detection for listeners with severe high-frequency hearing loss. International Journal of Audiology, 46, 293-308.

Please contact jason_galster@starkey.com with questions.

* Spectral iQ is a Starkey brand name.

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Plural Word Lists for the Validation of Frequency Lowering

Instructions for live voice validation

With frequency lowering deactivated, complete the following steps:

1. With mouth obscured, say a single word at a conversational level.

2. Ask the patient to repeat the word.

3. Mark the response as correct or incorrect, completing a single list.

4. Calculate the patient’s score (% correct).

With frequency lowering activated, use an alternate list and repeat steps 1-4. If the patient’s ability to detect the plural cues does not improve, increase Spectral iQ Bandwidth and Gain. Continue this process until the patient demonstrates an improvement in performance with Spectral iQ active.

LIST 1 SCORE LIST 2 SCORE LIST 3 SCORE

Key Play Coats

Days Ears Floor

Plays Keys Signs

Toy Clouds Eye

Cities Brick Book

Bricks City Frogs

Pig Way Boats

Cloud Toys Card

Ways Pigs Caves

Ear Day Pen

TOTAL TOTAL TOTAL

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LIST 4 SCORE LIST 5 SCORE LIST 6 SCORE

Coat Hat Cart

Floors Lists Shines

Sign Pear Cries

Eyes Carts Hats

Books Shine List

Frog Rats Guard

Boat Reeds Parts

Cards Guards Rat

Cave Part Reed

Pens Cry Pears

TOTAL TOTAL TOTAL

Notes

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