A particle separator for a fluid pump has a cylindrical body which is attachable to a pump by a flexible sleeve and has tangential slots directing intake fluid in swirling manner about an inlet tube within the cylindrical body. And, the high-refractive-index portion has first and second horizontal cross-section surfaces. In some embodiments, echo-reduction circuitry may insert a training signal into digital audio signals at or below a noise floor and in a non-audible portion of the frequency spectrum based on a spectral mask. A detent structure releasably holds the lock member in locking and unlocking orientations in which the lock member is prevented from moving parallel to the length of the connector member.