sˌoʊ ðə mˈæskɪŋ θɹˈɛʃoʊld ɪz ðə sˈaʊnd pɹˈɛʃɚ lˈɛvəl əvə sˈaʊnd nˈiːdᵻd tə mˌeɪk ðə sˈaʊnd ˈɔːdᵻbəl ɪnðə pɹˈɛzəns ʌv ɐnˈʌðɚ nˈɔɪz kˈɔːld ˈeɪ "mˈæskɚ".
So the masking threshold is the sound pressure level of a sound needed to make the sound audible in the presence of another noise called a "masker".