## 3 Procedures and Material
### Suppressor's Pattern Specification  
The suppressor's pattern is determined on the grounds of auditory excitation and loudness of the rTMS click acoustic patterns [15; 16]. Figure 3: Typical rTMS click waveform in (**a**), and octave-band spectra of acoustic noise excitation (dashed line) and equivalent acoustic excitations of vibratory component (colored solid lines) when using layers of various materials between the coil and skull in (**b**). Figure 2: Procedure for the estimation of hearing stimulation pattern. More specifically, the sequence of rTMS-click's acoustic pattern is converted to an equivalent auditory excitation and, subsequently, to a spectrotemporal loudness pattern \(A(f)\)[17; 18; 19], namely \(A(t,f)=T[rtms(t)]\), where \(T[. ]\) is the process of time-varying loudness computation and \(rtms(t)\) is the rTMS-click sequence. The suppressor's spectral density \(S_{or}(f)\) is determined from \(A(t,f)\) so that its estimated loudness is \(L_{S_{or}}(f)\simeq max_{t}(A(t,f))\)[16]. The finer specification of the suppressor pattern's main characteristics is performed individually for each patient (Figure 4) by a specially designed software module, which spectrally reshapes (for each individual subject) the output of the suppressor's core perceptual computation and generation module, and it determines optimal ranges of stimulation parameters through an adaptive psychophysical optimization. Various factors which can cause deviations from the initially designed pattern of the suppressor mandate the fine tuning of its parameters for optimal individualized adaptation. Among others, such factors can be:  
* Intersubject variability of external ear's acoustics and deviations from the measured rTMS-click pattern at the concha of the standard torso simulator's pinna. * Intersubject variability in perceptual sensitivity of rTMS-click detection under the concurrent presentation of the suppressor. * Intersubject variability in the perception of loudness of the suppressor and/or the rTMS-click due to binaural presentation. * Variability due to earphones insertion and fit into the ear canal. The individualized wide-band noise (WBN) masking stimulus is psychophysically fine-tuned (matched) so that the subject does not detect any repetitive TMS sound when presented with both the suppressor and the rTMS stimulation. The fine tuning of the suppressor determines the optimal values of three parameters that modify the suppressors spectral pattern:  
* parameter \(f_{shift}\) for frequency shifting of the whole pattern, namely \(L_{S_{or}}\big{(}f-f_{shift}\big{)}\)
* spectral slope parameter \(slope_{dB/oct}\) around the frequency of maximum \(L_{S_{or}}(f)\), namely \(f_{max}=argmax_{f}(L_{S_{or}}(f))\), and
* overall gain \(G\) which accounts for overall loudness adjustment. The final log spectral density of the suppressor is  
\[S_{final}(f)=S_{or}(f-f_{max})-\frac{slope_{dB/oct}}{3}*10 log_{10}\bigg{(} \frac{f_{max}}{f}\bigg{)}+G,\]  
where \(S_{or}(f)\) is the initial log spectral density of the suppressor in dB. The frequency shifting parameter \(f_{shift}\) and the spectral slope parameter \(slope_{dB/oct}\) are allowed to vary in the intervals \([-500...500]\) Hz and \([-6...+6]\) dB/oct, respectively. The complete psychophysically matched wide-band noise (WBN) masking stimulus determination is conducted through a specially designed Psychophysical Coordination software (based on National Instruments' LabVIEW), which is used for the realization of an adaptive procedure for optimal placement of suppressor's parameters, thus targeting both the subject's comfort and the degree of AEP reduction. The adaptive psychophysical procedure, in a sequence of runs, for each of several pairs of the frequency shifting and the spectral slope parameters, determines the minimum value of the gain parameter that satisfies non-audibility of the rTMS sequence, using an adaptive stair-case procedure [20].