An audio system, comprising: a headset, comprising: a housing configured for forming a cavity along with an external auditory canal of an ear (RE, LE) when the headset being mounted on the ear (RE, LE); a speaker disposed in the housing; and a microphone disposed in the housing; and a control device, coupled to the headset, wherein the control device is operable to: provide a reference audio signal to the speaker to be broadcasted toward the cavity; receive a sampled sound signal through the microphone from the cavity corresponding to a reflection of the reference audio signal; calculate an acoustic intensity distribution curve over frequencies from the sampled sound signal; and determine whether the cavity has a leakage outlet according to the acoustic intensity distribution curve over frequencies; wherein the reference audio signal has a consistent level of acoustic intensity over frequencies; characterized in that the control device is further operable to: extract a portion of the acoustic intensity distribution curve under a reference frequency; map the portion of the acoustic intensity distribution curve to an approximate quadratic curve; and determine whether the cavity has the leakage outlet based on at least one coefficient of the approximate quadratic curve. a headset, comprising: a housing configured for forming a cavity along with an external auditory canal of an ear (RE, LE) when the headset being mounted on the ear (RE, LE); a speaker disposed in the housing; and a microphone disposed in the housing; and a housing configured for forming a cavity along with an external auditory canal of an ear (RE, LE) when the headset being mounted on the ear (RE, LE); a speaker disposed in the housing; and a microphone disposed in the housing; and a control device, coupled to the headset, wherein the control device is operable to: provide a reference audio signal to the speaker to be broadcasted toward the cavity; receive a sampled sound signal through the microphone from the cavity corresponding to a reflection of the reference audio signal; calculate an acoustic intensity distribution curve over frequencies from the sampled sound signal; and determine whether the cavity has a leakage outlet according to the acoustic intensity distribution curve over frequencies; provide a reference audio signal to the speaker to be broadcasted toward the cavity; receive a sampled sound signal through the microphone from the cavity corresponding to a reflection of the reference audio signal; calculate an acoustic intensity distribution curve over frequencies from the sampled sound signal; and determine whether the cavity has a leakage outlet according to the acoustic intensity distribution curve over frequencies; wherein the reference audio signal has a consistent level of acoustic intensity over frequencies; characterized in that the control device is further operable to: extract a portion of the acoustic intensity distribution curve under a reference frequency; map the portion of the acoustic intensity distribution curve to an approximate quadratic curve; and determine whether the cavity has the leakage outlet based on at least one coefficient of the approximate quadratic curve. extract a portion of the acoustic intensity distribution curve under a reference frequency; map the portion of the acoustic intensity distribution curve to an approximate quadratic curve; and determine whether the cavity has the leakage outlet based on at least one coefficient of the approximate quadratic curve.