Table 3. Description of methodological parameters, results, and conclusion of the included studies.

Studies	Methodological parameters						Main results	Conclusion
	Recording equipment	Stimulus	Noise	Form of presentation	Acquisition parameters	Registered potentials
Androulidakis and Jones (2006) 19	Virtual oscilloscope (Pico Technology, St Neots Cambridgeshire, United Kingdom).	Pure tone of 200 ms, 61 dB SPL, and frequency of 1 kHz.	a) Unmodulated random noise (80 dB SPL; broadband: 0–20 kHz). b) Random noise modulated in amplitude by a square wave of 17.5 Hz.	Electromagnetic earphone (Sanyo, PH230, Moriguchi, Osaka, Japan) in both ears.	Six silver electrodes in Fpz, Fz, Cz, and Pz C3 and C4 (impedance < 5 kΩ). Window (700ms); filter (1 Hz and 200 Hz).	Amplitudes and latency of the N1 and P2 components.	The N1 and P2 components were statistically higher and earlier in the modulated noise condition compared with the unmodulated noise condition. The latencies were strongly determined by whether the tones coincided with the rise or fall of the modulated masking envelope (instant noise level was low).	Masking release is correlated with waves N1 and P2. Furthermore, it is possible that the responses of these components to modulated and unmodulated masking can assess auditory temporal resolution processes, which are a crucial part of complex sound perception.
Epp et al. (2013) 14	Recording cortical potentials with EEG, with measurement (BIOSEMI ActiveTwo, Amsterdam, Netherlands) and attenuation system (Tucker-Davis Technologies, Alachua, FL, United States).	300 ms pure tone, 70 dB SPL and 700 Hz frequency.	Wideband noise (1,000ms) presented at different SNR randomly (-15, -5, +5, +15 dB) and in two conditions: a) noise modulated at 700 Hz with intensity fluctuation centered on the signal; b) non-modulated noise with frequencies not centered on the signal (300, 400, 1,000 and 1,100 Hz).	ER-2 insert earphones (Etymotic Research, Inc., Elk Grove Village, IL, United States) in both ears.	64 silver chloride electrodes, with the CZ electrode as a reference. The electrodes (A1, A2 and Iz) recorded the peaks of auditory potential responses. Window (700 to 1,250ms); filter (0 and 200 Hz).	Amplitudes of components N1 and P2.	The N1 amplitude showed very similar values for both types of masking (modulated and unmodulated). P2 amplitudes were higher for the modulated masking condition. Higher peak-to-peak amplitude of N1-P2 in modulated masking condition.	The P2 component is a candidate for an objective measure of audibility in the human auditory system. The P2 amplitude is consistent with the psychoacoustic findings of masking release.
Zhang et al. (2014) 15	Recording of cortical potentials (64-channel SynAmps, Compumedics NeuroScan, Melbourne, Australia).	a) Syllable /bi/ (target stimulus) of 474 ms, 60 dB SPL and frequency of 254 Hz. b) Syllable /di/ (frequency of 258 Hz) as a stimulus to probe the participants' attention.	a) Constant/steady noise. b) Modulated speech spectrum noise (SNR of −4 dB) and 50–150 Hz. c) Noise from two speakers (informational)	Insert headphones in both ears.	Six electrodes, being recorded at the Cz site, amplitudes and latencies of the N1/P2 components. Window (1,000–1,200ms); filter (0 Hz and 200 Hz).	Amplitudes and latency of the N1 and P2 components.	Under the conditions of passive and active listening, separately, the amplitudes were significantly higher in the conditions of steady and modulated masking, compared with the condition of informational masking. As for latencies, N1/P2 shortening was observed in the presence of constant noise in the passive listening condition and in the face of informational noise in the active listening condition.	Informational noise induced a much greater masking effect in the N1/P2 complex, suggesting that this type of masking, induced by irrelevant speech of speech signals, occurs in the early stages of cortical processing. Masking release should not be associated with attentional processes; it can be explained as a neurophysiological process.
Maamor and Billings (2017) 16	Recording of cortical potentials (Synamps RT/Scan, Compumedics NeuroScan, Melbourne, Australia) and a 64-channel electrode cap.	Syllable /ba/ and /da/, 150 ms and 65 dB SPL. Passive oddball paradigm, presentation of the pattern /ba/ of 0.8 and the deviant /da/ of 0.2.	Three types of background noise at three different SNRs: -3, 3 and 9 dB. All the noises were low-pass filtered at 4,000 Hz. a) Continuous speech noise. b) Modulated noise. c) Babbling of 4 speakers.	The signals were presented monaurally to the right ear.	The reference electrode (Cz) was located at the vertex and the ground electrode was placed on the forehead. Window (100–1,000ms); filter (0 Hz and 100 Hz).	Amplitudes and latency of components P1, N1, and P2.	A systematic decrease in amplitude and increase in latency in the cortical components was observed in the continuous noise condition, given the effect of SNR. Modulated noise contains spectral energy similar to continuous noise, but with variations in the temporal envelope.	The little interference of the SNR effect in the modulated noise condition can be explained by the fluctuations/gaps in the modulated noise, making the signal audible, regardless of the noise level. It is concluded that the spectrotemporal characteristics of signals and noises play an important role in determining the morphology of neural responses.
Tanner et al. (2019) 17	Recording of cortical potentials (SynAmp RT, Compumedics NeuroScan, Melbourne, Australia) synchronized with the Tucker-Davis Technologies (Alachua, FL, United States) stimulation system.	Syllable /ba/ of 80 ms, 40 dB SPL and frequency of 1 kHz.	Speech spectrum noise in 4 conditions: a) low steady noise (30 dB SPL); b) high steady noise (65 dB SPL);. c) modulated noise at an intensity of 65 dB SPL and 30 dB SPL with a modulation rate of 6.25 Hz (slow modulated); d) modulated noise at an intensity of 65 dB SPL and 30 dB SPL with a modulation rate of 25 Hz (fast modulated).	Electromagnetically shielded earphones (ER2, EtymoticResearch, Inc., Elk Grove Village, IL, United States ), in both ears.	4 silver chloride electrodes: A1 and A2 (ear lobes), Fpz (high forehead line) ,and Cz (skull vertex). (Impedance ≤ 5 kΩ and ≤ 3 kΩ between electrodes.) Window (-100 to +300ms); filter (1 Hz and 100 Hz).	Amplitude and latency of the P1-N1-P2 complex.	The mean electrophysiological threshold in modulated masking was ∼ 13.5 dB lower than in the steady masking, resulting in masking release. It was observed that, for the different types of noise, as the SNR decreases, the general amplitude of the P1-N1-P2 response decreased, and the peak latencies increase – mainly that of N1.	Electrophysiological measures of masking release using CAEP with speech stimuli correspond to behavioral estimates for the same stimuli. It is suggested that objective measures based on electrophysiological techniques can be used to reliably assess aspects of temporal processing capacity.
Rocha et al. (2022) 18	Recording of cortical potentials (IHS equipment, Intelligent Hearing Systems, Miami, FL, United States) with the Tucker-Davis Technologies (Alachua, FL, United States) stimulation system.	Syllable /ba/ of 80 ms, 65 dB SPL and presentation rate of 3.8.	Speech spectrum noise in 3 conditions: a) weak steady noise (30 dB SPL); b) strong steady noise (65 dB SPL); c) modulated noise at an intensity of 65 dB SPL and 30 dB SPL with a modulation rate of 25 Hz.	Electromagnetically-shielded earphones (ER2, EtymoticResearch, Inc., Elk Grove Village, IL, United States) in the right ear.	4 electrodes: A1 and A2 (ear lobes), Fpz (high forehead line) and Cz (skull vertex). (Impedance ≤ 5kΩ.) Window (512ms); filter (1 Hz and 30 Hz).	Amplitude, latency, and morfology of the P1-N1-P2 complex.	P1 and N1 showed higher latencies in the stable noise condition. More robust amplitudes of the P1-N1-P2 complex were recorded in the modulated noise condition, with statistical significance. The mean electrophysiological thresholds were higher in the stable noise condition (60 dB SPL), with an average difference of 11.7 dB higher than in the modulated noise condition.	There was a lower masking effect of modulated noise when compared with the strong steady noise condition, in the amplitude measurements of the P1-N1-P2 complex. The mean difference of 11.7 dB between the electrophysiological thresholds (under conditions of stable noise and modulated noise) was interpreted as the masking release measure.

Abbreviations : CAEP, Cortical auditory evoked potential; EEG, electroencephalography; SNR, signal-to-noise ratio.