HiFi Mobile Phone Audio Testing
Mobile phones featuring High Fidelity (HiFi) technology experienced significant growth in 2014 and have driven increases in new product development, with manufacturers replacing conventional codec chips with advanced 192KHz/24-bit DAC and op-amp chips. Through audio, op-amp and other chips, sound quality of mobile phones can compare to 4X CD quality. HiFi technology will continue to be widely applied in mobile phones. As audio performance and quality are enhanced, challenges grow in audio testing. Upgraded function tests are required and can be realized by replacing low-end sound cards with more high-end audio test hardware.
Currently, commercially available sound cards (THD+N: -80 to -90dB, Noise level: 20 to 50µVrms) are unable to satisfy the demands of HiFi measurement, such that manufacturers are required to access suitable 24-bit high precision, low distortion and low noise audio acquisition cards for production line testing with requirements are as follows:
- Noise level referred to input < 3µVrms
- THD+N (20Hz – 20KHz) referred to input < -95dB
HiFi Mobile Phone Testing Items:
- Noise level testing: Acquisition of earphone output noise signals to verify compliance with specification, with standard values varying according to mobile phone model, normally 3 to 5µVrms.
- THD+N testing: Acquisition of earphone output single-tone signals at different frequencies (20Hz to 20KHz) to verify compliance of THD+N with specification, with standard values will varying according to mobile phone model, normally -90dB to -100dB.
For HiFi mobile phone audio quality testing, ADLINK provides the PCI-9527, connecting the phone's left and right sound tracks through its two analog input channels. After input measurement range is set at ± 0.316V, the PCI-9527 measures earphone output and compares the acquired values with original design specs, to evaluate DUT noise level. Further adjusted is input measurement according to the mobile phone's THD+N testing requirement, and earphone output single-tone signals are then tested at different frequencies (20Hz to 20KHz) using FFT to obtain THD+N measured values. Finally, DUT is tested for compliance with HiFi design standards.
The PCI-9527 provides 24-bit high precision and ultra-low distortion, accepting input signals as low as 3µVrms and input THD+N (1KHz) to more than 100dB. Compared with standard sound cards often limited to measuring THD in -80dB or -90dB ranges, the PCI-9527 thoroughly fulfils key indicators in HiFi-enabled mobile phone testing, making it a clear market leader.