Automatic Maximum Sound Pressure Level (SPL) Measurements Inside Cars

Abstract: With a growing interest in technical specifications among consumers, there is a need for accessible measurement tools that enable individuals to evaluate the performance of their equipment, including common speakers and car audio systems, beyond what the manufacturer provides. However, the existing measurement systems are often geared towards professionals. This thesis aims to address this gap by designing and developing a user-friendly measurement tool that empowers individuals to easily measure and evaluate the performance of their devices. The work started with identifying the key technical specifications that users are interested in, and three parameters were selected for estimation: the maximum sound pressure level the system can provide, the corresponding multi-tone distortion and total harmonic distortion. Each parameter's measurement method varies, particularly in the choice of test stimuli and data processing. The methods in this thesis were determined after comparing existing standards for acoustical output-based measurement. Furthermore, some problems in terms of measurement capabilities and accuracy when implementing measurements within the defined application scenarios were also discussed. Ideally, the tool can finally provide users with detailed insights into chosen technical specifications, allowing them to know their audio systems better and make informed decisions. The automatic control of playback and recording as well as the processing afterwards was implemented in Python with the help of some existing packages. A graphic user interface based on PyQt was also developed to improve the manipulation of the measurement. Thus, the functionality that the tool is supposed to have is initially fulfilled, although its accuracy needs further verifying and improvement and the scope of the tool can be extended.