Etymotic The BEAN® Quiet Sound Amplifier® - Manual (Page 10)

IMPORTANCE OF A DEEP SEAL
English
Note: QSA devices come with a large selection of eartips, including two sizes of 3-flange
eartips with long stems. Depending on your ear geometry, the longer stems may allow
the deepest seal.
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A deep eartip seal ensures the best performance and prevents
the “hollow voice” sound, called the occlusion effect.
• The occlusion effect is caused by sound transmission into the ear from
vibration of the ear canal wall when the ear is occluded by an eartip.
• The vibration comes from sound pressure developed in the back
of the mouth.
• The occlusion effect is most commonly caused by vibration from a
person’s own voice, especially from speaking the sounds “ee” and “uu,”
or from playing a brass or woodwind musical instrument.
• The occlusion effect is worse when there is a shallow insertion
of the eartip.
• Deeply-sealed eartips reduce the occlusion effect.