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.
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.
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.
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:
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.
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.