Electroacoustic measurements on cellular telephones
John R. Bareham · The Journal of the Acoustical Society of America · 1999
The fundamental electroacoustic frequency response measurements on cellular telephones are send, receive, sidetone, and echo. Loudness ratings are calculated from these measurements. Measurements can be made by using a test instrument incorporating a vocoder, a reference base station, a digital audio interface, an actual telephone call, or by testing the phone in loopback mode. In each case, the measurement is calibrated in terms which relate to the public telephone network. Selection of test signals such as sine wave, pink noise, or artificial speech can influence the results. The ear simulator used to measure the receiver can be a sealed complex cavity, sealed but including a defined leak, or a complex cavity plus an anthropomorphic pinna. The choice of ear simulator dramatically influences the results of receiver measurements. Send response is usually measured in close proximity to a standard mouth simulator, but can also be measured in a diffuse sound field to assess pickup of room noise. Hands-free kits pose special measurement challenges which will be briefly reviewed. Key national and international standards associated with electroacoustic measurements on cellular telephones will be cited.