Depending on your hearing loss, hearing aids typically help make speech over the telephone clearer. If you are on the telephone a lot, consider getting hearing aids with the "T" (telecoil) circuits described above. Telephone sounds are amplified more efficiently and background noises are better eliminated with this kind of circuit. [Only some cordless telephones work well with hearing aids].
People with hearing loss may also benefit from a telecoil to use with some of the special assistive listening sound systems available in many auditoriums, theaters and other public places as required under federal law. Discuss your option of a "T" switch with your audiologist.