MICROPHONE ASSEMBLY WITH ACOUSTIC FILTER

The present invention relates to a microphone assembly with an acoustic filter. The invention may e.g. be used to reduce undesired influence of ultrasound in the environment on audio signals picked up by hearing aids, headsets, and other listening devices.The microphone assembly comprises a microphone (101) with a first acoustic port (106), wherein the microphone (101) is configured to convert acoustic waves received through the first acoustic port (106) into an electric signal. The microphone assembly comprises a filter housing (110) with a second acoustic port (117) and a rim (119). The microphone assembly comprises a carrier (102, 103, 120) attached to the microphone (101) and to the rim (119) of the filter housing (110) such that the carrier (102, 103, 120) and the filter housing (110) together enclose a cavity with a first acoustic passage (121) fluidly connecting the first acoustic port (106) and the second acoustic port (117) thereby enabling acoustic waves to propagate from the second acoustic port (117) through the first acoustic passage (121) to the first acoustic port (106).The invention is characterized in that the carrier (102, 103, 120) and the filter housing (110) are configured to cause the cavity to comprise an acoustic chamber (111) and a second acoustic passage (112), wherein the second acoustic passage (112) has a first opening into the first acoustic passage (121) and a second opening into the acoustic chamber (111) such that the acoustic chamber (111) and the second acoustic passage (112) together establish a Helmholtz resonator for suppressing acoustic energy within a first frequency band in acoustic waves propagating through the first acoustic passage (121).