# Optimization of Parametric Equalizer Filters in In-Vehicle Audio Systems with a Genetic Algorithm
## 1 Introduction  
Listening to music while driving, one of the most common activities, not only serves as a source of entertainment for drivers and passengers but also significantly impacts driving comfort and overall fatigue levels. Studies demonstrate that in-car sound has a direct effect on the driver's comfort and fatigue levels [1]. In this context, the quality of in-car sound emerges as a critical factor that influences substantially the experience of both drivers and passengers. With the advancement of technology, vehicle manufacturers and audio system designers develop various strategies to meet users' expectations and improve the systems regarding sound quality, aiming to minimize driver fatigue. The impact of in-car sound quality on the listening experience is evaluated within the framework of sound engineering and psychoacoustic principles [2]. Particularly, the compatibility of sound characteristics from speaker output with the equal-loudness contour, which reflects the human ear's varying sensitivity to frequencies between 20 Hz and 20 kHz, is critical for the clarity and accuracy of sound [3]. The adequacy within this frequency range provides a detailed and rich audio experience, enhancing the comfort and enjoyment of drivers and passengers. Moreover, studies indicate that systems incompatible with the equal-loudness contour negatively affect drivers' fatigue and stress levels during long-distance trips. This situation significantly impacts drivers' attention and reaction times,thereby endangering overall road safety [4]. Therefore, optimizing in-car sound systems based on this contour plays a critical role not only in enhancing the driver and passenger experience but also in maximizing road safety. In vehicle audio systems, it is required that the different frequency ranges be meticulously adjusted to ensure that the speaker output aligns with the equal-loudness contour. This tuning is carried out with equalizers that are used to adjust the level of sound signals within specific frequency ranges. There are three types of equalizers: graphic equalizers, parametric equalizers, and digital equalizers. The graphic equalizer allows users to adjust sound levels manually at predefined frequency bands. The digital equalizer, utilizing sophisticated technology, automatically adjusts the sound profile based on factors such as vehicle speed and engine noise, catering to advanced driver assistance systems. The parametric equalizer is a highly adjustable audio processing filter used to modify the amplitude of sound signals within certain frequency ranges. This filter provides precise control over three parameters: center frequency, gain, and quality factor (Q factor). The detailed control capability makes the parametric equalizer particularly suitable, compared to other options, for tuning the speaker output according to the equal-loudness contour, making it preferable in vehicle multimedia systems [5]. The in-car sound system is a complex structure comprising various components, such as the vehicle multimedia system, amplifiers, speakers, cables, and connectors. Although each component affects the frequency response throughout the system in various ways, the speakers make the most critical modifications. Since a single speaker cannot deliver perfect performance across all frequencies, quality sound systems employ speakers together, designed for different frequency regions. Modern vehicles include a wide variety of speakers such as subwoafers, woofers, mid-ranges, full-ranges, and tweeters. Each of these speakers offers different responses in specific frequency ranges; thus, in the optimization of vehicle audio systems, equalizer settings need to be meticulously addressed for all types of speakers [6]. In vehicle multimedia systems, tuning filter parameters to conform to the equal-loudness contour and measuring speaker output with a sound analyzer are fundamental steps in optimization.