In a lift. Towards the centre of a large concrete-steel building. It is recommended that hearing aid users test the CDMA mobile phone technology with their hearing aid before finalising any purchase agreement. CDMA mobile displays indicate whether the area has strong or weak reception. Typically four or five bars are used to indicate strong reception and one bar is used to indicate weak reception.
Hearing aids are more prone to experience interference in weak reception areas.
Move towards the centre of the building to seek out a weak reception area and dial a known phone number to test the mobile. It may be necessary to move out of the store to find a weak reception area. Under these conditions if interference is not perceived, or is just perceptible, then the hearing aid will be compatible with the CDMA mobile phone. If interference is perceived as being annoying then an accessory may be required to create some distance between the hearing aid and mobile phone. Also angling the handset slightly upwards may also reduce the feedback whistling sound.