The BKB-SIN is a speech-in-noise test that uses BKB (Bamford-Kowal-Bench) sentences, recorded in four-talker babble. The BKB-SIN can be used to estimate SNR loss in children and adults for whom the QuickSIN test is too difficult.
- Quick and easy to administer and score
- Age-related norms for children
- Suitable for cochlear implant users
- Appropriate for adults with auditory memory difficulties
Methodology
BKB-SIN Methodology
The BKB-SIN contains 18 List Pairs that are equated for difficulty. Each List Pair has two lists; both lists of the pair must be administered, and the scores averaged, for valid scoring. Each List Pair takes approximately three minutes to administer and score. Results are compared to normative data to obtain the SNR Loss.
- List Pairs 1-8 have ten sentences in each list, with one sentence at each SNR of: +21, +18, +15, +12, +9, +6, +3, 0, -3 and -6 dB. These List Pairs can be used with all listeners.
- List Pairs 9-18 have eight sentences in each list, with one sentence at each SNR of: +21, +18, +15, +12, +9, +6, +3 and 0 dB. These provide ten additional equivalent List Pairs that can be used for cochlear implant patients and those with significant SNR loss. These lists are not recommended for normal-hearing listeners, since a test floor effect will occur.
Scoring
A verbal "ready" cue precedes each sentence. The first sentence in each list has four key words, and the remaining sentences each have three. Key words are underlined on the score sheets.
- Give one point for each key word repeated correctly. Put the total correct for each sentence on the line provided.
- Subtract the total correct for each list from 23.5 to obtain the SNR-50 (signal-to- noise ratio for 50% correct).
- Average the SNR-50 scores for both lists of the List Pair. When administering more than one List Pair, average the List Pair scores.
- Compare the List Pair score to the age-related norms to determine SNR Loss.
What is SNR Loss?
SNR loss is the increased signal-to-noise ratio required by a listener to understand speech in noise, as compared to normal performance. On the BKB-SIN Test normal-hearing adults obtain 50% correct at a -2.5 dB SNR. We call this the SNR-50. A hearing- impaired adult with an SNR-50 score of 7.5 dB would have a 10 dB SNR Loss [7.5 - (- 2.5) = 10]. The measurement of SNR loss is important because it cannot be reliably predicted from the pure tone audiogram.
Performance on any speech-in-noise test is affected by a number of factors, including:
- Speech materials (sentences, spondees, etc.)
- Background noise (shaped noise, multi-talker babble)
- Test setup (combined speech and noise vs. separated speech and noise)
- Audibility of the signal
- Reverberation
- Knowledge of the language
- Subject age
Due to these factors, absolute scores for an individual subject will vary across different speech-in-noise tests. BKB-SIN Test scores are reported in SNR Loss because it is substantially independent of calibration and test material. Calibration and/or test material differences that affect SNR-50 values equally for normal and hearing-impaired listeners will "cancel out" in the SNR Loss calculation.
Knowing the SNR loss allows the hearing professional to recommend the appropriate technology (e.g., omni-directional microphones, directional microphones, array microphones, FM systems) required for the listener to function in noisy situations. Knowing the SNR loss also enables the hearing professional to give the patient realistic expectations for their potential improvement in noise with a given technology, which often reduces unnecessary visits for hearing aid re-adjustments after the fitting.
Interpreting test results for children should be done on a case-by-case basis. Results should not be interpreted in isolation, but rather be integrated with other information regarding a child's speech/language abilities, educational performance and ability to function in the classroom. See "Test Interpretation (children)" in the BKB-SIN Test manual for more information.
CPT Codes
At present, no CPT code exists for speech-in-noise tests performed to determine SNR Loss. Practitioners who submit for reimbursement use CPT 92700 (Unlisted ENT Service or Procedure). Using this code requires a narrative describing the procedure and its purpose, as well as substantiation from the literature.
- Reimbursement is typically fair.
- If the third-party payer is a private carrier (such as a PPO), the practitioner could meet with the insurance company to negotiate a fee for the procedure. The insurance company would then assign its own code for this procedure.
- Alternatively, the practitioner may choose to bill the patient for the procedure as a non-covered benefit, providing they discuss the charges with the patient prior to testing.
