Investigating the effects of sound masking on the use of audio CAPTCHAs
Abiodun Olalere, Jinjuan Heidi Feng, Jonathan K. Lazar, Tim Brooks · Behaviour and Information Technology · 2014
The SoundsRight Audio Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHA) was developed with the goal of providing a usable and secure audio CAPTCHA for people with visual impairments. Its design requires users to repeatedly identify a specific sound from a group of different sounds (e.g. baby crying and bird chirping) in real time. Adding background noise (sound masks) to the sounds may make it more difficult for automated software to recognise the sounds and therefore, improve security. However, the sound masks may also make it more challenging for human users to recognise the sound. We conducted a user study involving 20 blind participants and 20 sighted participants to investigate the effect of sound masks on the usability of the SoundsRight CAPTCHA. The results suggest that sound masks do have a significant impact on the failure rate and response time. Sighted participants had significantly a higher failure rate than blind participants and were more vulnerable to the negative effect of sound masks.