A method for assessing an acoustical performance of an in-ear device using an apparatus comprising: - a controller unit operatively connectable to a sound source; - a user interface unit operatively connecting to said controller unit to allow a user to interface therewith by storing the predetermined acoustic attenuation (DPAA) of the acoustic damper therein; and - a sound measurement device operatively connecting to said controller unit, said sound measurement device being selectively locatable in a close relationship relative to the in-ear device and outside the ear canal for measuring a first sound level outside the ear canal when submitted to the sound source, said sound measurement device being removably engageable into the passageway to selectively occlude the passageway for measuring a second sound level inside the ear canal with the in-ear device inserted therein when submitted to the sound source; the in-ear device having a passageway extending therethrough for receiving an acoustic damper therein, the acoustic damper having a predetermined acoustic attenuation (DPAA) thereof, the passageway being in fluid communication with an ear canal of an ear when the in-ear device is inserted therein, said method comprising: a) - operatively connecting the controller unit to the sound source; - operatively connecting the user interface unit to said controller unit to allow a user to interface therewith by storing the predetermined acoustic attenuation (DPAA) of the acoustic damper therein; - operatively connecting the sound measurement device to said controller unit, said sound measurement device being selectively located in close relationship relative to the in-ear device and outside the ear canal for measuring the first sound level outside the ear canal when submitted to the sound source, said sound measurement device being removably engaged into the passageway to selectively occlude the passageway for measuring the second sound level inside the ear canal with the in-ear device inserted therein when submitted to the sound source; - using said controller unit for calculating an acoustical performance of the in-ear device with the acoustical damper inserted in the passageway thereof from a blocked acoustic attenuation obtained with said first and second sound levels (42,44) and the predetermined damper acoustic attenuation (DPAA). - a controller unit operatively connectable to a sound source; - a user interface unit operatively connecting to said controller unit to allow a user to interface therewith by storing the predetermined acoustic attenuation (DPAA) of the acoustic damper therein; and - a sound measurement device operatively connecting to said controller unit, said sound measurement device being selectively locatable in a close relationship relative to the in-ear device and outside the ear canal for measuring a first sound level outside the ear canal when submitted to the sound source, said sound measurement device being removably engageable into the passageway to selectively occlude the passageway for measuring a second sound level inside the ear canal with the in-ear device inserted therein when submitted to the sound source; a) - operatively connecting the controller unit to the sound source; - operatively connecting the user interface unit to said controller unit to allow a user to interface therewith by storing the predetermined acoustic attenuation (DPAA) of the acoustic damper therein; - operatively connecting the sound measurement device to said controller unit, said sound measurement device being selectively located in close relationship relative to the in-ear device and outside the ear canal for measuring the first sound level outside the ear canal when submitted to the sound source, said sound measurement device being removably engaged into the passageway to selectively occlude the passageway for measuring the second sound level inside the ear canal with the in-ear device inserted therein when submitted to the sound source; - using said controller unit for calculating an acoustical performance of the in-ear device with the acoustical damper inserted in the passageway thereof from a blocked acoustic attenuation obtained with said first and second sound levels (42,44) and the predetermined damper acoustic attenuation (DPAA). - operatively connecting the user interface unit to said controller unit to allow a user to interface therewith by storing the predetermined acoustic attenuation (DPAA) of the acoustic damper therein; - operatively connecting the sound measurement device to said controller unit, said sound measurement device being selectively located in close relationship relative to the in-ear device and outside the ear canal for measuring the first sound level outside the ear canal when submitted to the sound source, said sound measurement device being removably engaged into the passageway to selectively occlude the passageway for measuring the second sound level inside the ear canal with the in-ear device inserted therein when submitted to the sound source; - using said controller unit for calculating an acoustical performance of the in-ear device with the acoustical damper inserted in the passageway thereof from a blocked acoustic attenuation obtained with said first and second sound levels (42,44) and the predetermined damper acoustic attenuation (DPAA).