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. Author manuscript; available in PMC: 2018 Mar 1.
Published in final edited form as: Ear Hear. 2017 Mar-Apr;38(2):212–222. doi: 10.1097/AUD.0000000000000373

Figure 1.

Figure 1

Hypothetical spectral modulation transfer functions (SMTFs) for spectral ripple discrimination density threshold as a function of modulation depth. Symbols represent mean and +/− 1 standard error SRD thresholds for 8–11 year old normal hearing children and adults (from (Peter et al. 2014). SMTFs were derived using the function: f(x) = B*√((√(X/A))-1), where f(x) = the SRD ripple density threshold at ripple depth X, B is related to the inverse of the spectral filter width and A represents the modulation depth at f(x) = 0 (inverse of Eq 9 from Supin et al. 1999). The “mature” SMTF was fit using A = 1dB (from Supin et al. 1999) and the adult mean SRD threshold at 30dB depth (Peter et al. 2014). The “immature frequency resolution” SMTF was then fit using A = 1dB and the 8–11 year old mean SRD threshold at 30dB depth. The “immature intensity resolution” SMTF was fit by using the derived value of B for the “mature” SMTF and mean SRD threshold at 30dB. Relative to mature listeners, listeners with immature across-channel intensity resolution should have parallel SMTFs with a greater x-intercept whereas listeners with immature frequency resolution would have a flatter SMTF along the frequency axis.