A comparison of different methods to measure the EGG contact quotient.

The results from six published electroglottographic (EGG-based) methods for calculating the EGG contact quotient (CQEGG) were compared to closed quotients derived from simultaneous videokymographic imaging (CQKYM). Two trained male singers phonated in falsetto and in chest register, with two degrees of adduction in both registers. The maximum difference between methods in the CQEGG was 0.3 (out of 1.0). The CQEGG was generally lower than the CQKYM. Within subjects, the CQEGG co-varied with the CQkym, but with changing offsets depending on method. The CQEGG cannot be calculated for falsetto phonation with little adduction, since there is no complete glottal closure. Basic criterion-level methods with thresholds of 0.2 or 0.25 gave the best match to the CQKYM data. The results suggest that contacting and de-contacting in the EGG might not refer to the same physical events as do the beginning and cessation of airflow.