Masking threshold within acoustics (a branch of physics that deals with topics such as vibration, sound, ultrasound , and infrasound), refers to a process where if there are two concurrent sounds and one sound is louder than the other, a person may be unable to hear the soft sound because it is masked by the louder sound.
mˈæskɪŋ θɹˈɛʃoʊld wɪðˌɪn ɐkˈuːstɪks ɐ bɹˈæntʃ ʌv fˈɪzɪks ðæt dˈiːlz wɪð tˈɑːpɪks sˈʌtʃ ɐz vˌaɪbɹˈeɪʃən, sˈaʊnd, ˌʊltɹɐsˈaʊnd , ænd ˌɪnfɹəsˈaʊnd, ɹᵻfˈɜːz tʊ ɐ pɹˈɑːsɛs wˌɛɹ ɪf ðɛɹˌɑːɹ tˈuː kəŋkˈɜːɹənt sˈaʊndz ænd wˈʌn sˈaʊnd ɪz lˈaʊdɚ ðɐn ðɪ ˈʌðɚ, ɐ pˈɜːsən mˈeɪ biː ʌnˈeɪbəl tə hˈɪɹ ðə sˈɔft sˈaʊnd bɪkˈʌz ɪɾ ɪz mˈæskt baɪ ðə lˈaʊdɚ sˈaʊnd.