Performance evaluation of speech masking design among listeners with varying language backgrounds

•Six types of background noise were used as maskers: Pink, Babble, Time-reversed speech with randomly re-ordered frames (T-rev), T-rev with artificial reverberation (Trev + Reverb), Time-reversed speech using overlap-and-add (OLaW), and OLaW with artificial reverberation (OLaW + Reverb).•Some maskers showed clear differences in their effectiveness of masking speech towards native and non-native listeners.•Within the non-native listeners, higher proficiency did not result in lower masking effects in masked speech.•Maskers generated using randomly re-ordered frames (T-rev and T-rev + Reverb) had higher masking effects but were also rated as more annoying.•Considering the balance of tradeoff between intelligibility and annoyance, OLaW and OLaW + Reverb maskers appear to be the most effective maskers for both native and nonnative listeners out of the six maskers. Speech masking is a technique used for protecting speech confidentiality, which is realised by adding maskers to cover target speech. Numerous studies have demonstrated the native and non-native differences in perceiving masked speech, but few have compared the effect of masker types from the perspective of effectiveness of speech privacy and their annoyance levels. This paper reports on the result of an English word perception task by native and non-native listeners where six types of maskers, both speech-like and non-speech-like, are implemented, as well as the annoyance levels of each masker. Natives, non-natives residing in an English-speaking country, and non-natives residing in a non-English-speaking country were tasked to write down sentences when masking sound was present, and also to rate the annoyance levels of the maskers. Results showed that language background significantly affected the performance of unmasked speech, the difference between the two non-native listeners became minimal in the presence of maskers, and maskers annoyed the listener groups differently, calling for a discussion in the selection of a universally effective masker to increase speech privacy.