Understanding Car Audio Systems and How to Measure Quality of Car Stereo

The car audio market is steadily growing, with a market size valued at $9.68 billion in 2023 and projected to reach $17.83 billion by 2032, at a CAGR of 7.1%, according to Fortune Business Insights. This growth is unsurprising, considering that music plays a central role in the driving experience for many. In fact, a report from IFPI shows that 70% of people prefer to listen to music while driving. Similarly, research by Mercedes-Benz reveals that nearly 72% of drivers can’t imagine a car ride without music, and for two out of three people, sound quality is a crucial factor.

While modern car audio systems have significantly improved, their quality can only be accurately assessed after they are installed in the acoustically complex environment of a vehicle cabin.

In this blog post, we’ll explore customer expectations, analyze current trends in the car audio industry, and outline our methodology for testing and validating car audio system quality. Specifically, we’ll discuss how measuring frequency response helps replicate the user experience and ensure optimal sound performance.

What do customers expect from their car audio system? 

Surprisingly, new car buyers are willing to pay extra for better sound systems, making premium audio no longer exclusive to luxury brands. A recent survey found that over 70% of consumers want a high-quality audio system in their next car. To meet this demand, automakers are bringing premium sound into the mainstream.

As car prices rise, consumers expect more, especially considering the price. To stay competitive, automakers must offer high-end audio options across all price points.

Car brand perceptions illustrate this trickle-down effect. As shown in the graph above, the top 10 car brands most associated with high-end audio by consumers worldwide include Honda and Toyota—surpassing even luxury brands like Lexus and Cadillac in this regard.

However, it’s important to note that the survey sample size is relatively small, making it difficult to draw definitive conclusions. Additionally, customer perception of car brands can be highly subjective.

The vast majority of survey participants emphasized that, when it comes to high-end audio, sound quality matters more than flashy specifications. Consumers prioritize features like surround sound, active noise cancellation, and premium audio quality over speaker count or wattage. Notably, about 33% of respondents are unsure of the wattage they would prefer in their next sound system.

Car audio industry trends

As new technology and innovations are constantly being introduced into the automotive audio industry, some major trends and developments have been seen in recent years such as:

• Enhanced sound processing and high-resolution audio support
• Quieter interiors
• Multi-zone audio systems and customizable sound profiles

1. Enhanced sound processing and high-resolution audio support 

Digital signal processing (DSP) technology, introduced in the 1990s, has steadily improved, allowing for more precise tuning of bass, midrange, and treble frequencies. Modern systems support high-resolution audio formats and aim to create an immersive sound experience. Technologies such as Dolby Pro Logic II, Dolby Atmos, and DTS:X bring three-dimensional soundscapes into vehicles.

A survey shows that 71% of consumers consider surround sound essential, with 3D surround sound being the next major demand. This technology enhances depth, and width, and adds a sense of height to the sound, now featured in premium systems from Meridian, Bose, Harman, Burmester, and Bang & Olufsen.

Target curves are used by manufacturers to fine-tune car audio systems to ensure balanced, high-quality sound. The most widely accepted is the Harman curve, designed specifically for car interiors. Listeners tend to fall into three categories:

• Harman curve enthusiasts (64%) – Mostly under 50, they prefer a balanced sound aligned with the Harman standard.
• Bass lovers (15%) – Primarily young males, they favor stronger bass (3–6 dB boost below 300 Hz and +1 dB above 1 kHz).
• Less bass preference (21%) – Often older listeners and females, they prefer reduced bass (2–3 dB below 300 Hz and -1 dB above 1 kHz).

2. Quieter interiors

Manufacturers today focus on reducing wind and road noise while enhancing overall cabin insulation. Two main approaches are used to minimize interior noise:

• Passive noise cancellation (PNC). A physical method that involves using specialized materials to absorb and dampen unwanted sound waves. This approach is particularly effective at reducing high-frequency noise above 800 Hz.
• Active noise cancellation (ANC). A more recent innovation, ANC uses microphones, loudspeakers, and semiconductor components to counteract background noise. The microphones detect interior sounds, sending signals to an audio subsystem that processes them in real time using advanced digital signal processing (DSP) and adaptive algorithms. The system then emits an out-of-phase “anti-noise” signal through the car’s speakers, effectively canceling the original noise.

The graph above illustrates the effective frequency ranges and the noise attenuation that can be achieved using the ANC and PNC approaches.

While PNC excels at reducing high-frequency noise, ANC is more effective at suppressing low-frequency sounds (below 1 kHz). At lower frequencies, ANC offers superior noise reduction compared to PNC, making it the preferred solution for eliminating engine hum and road vibrations.

3. Multi-zone audio systems and customizable sound profiles 

To personalize the audio experience, modern systems allow users to create and save custom sound profiles. High-end automotive audio systems also support multi-zone functionality, enabling multiple passengers to listen to different audio settings simultaneously.

In multi-zone systems, sound staging isn’t determined solely by the physical placement of speakers or crossover design but is primarily shaped through Digital Signal Processing (DSP) adjustments. Two main philosophies influence car audio imaging:

• The European approach. Focuses on positioning the soundstage directly behind the steering wheel for a driver-centric experience.
• The U.S. approach. Centers the soundstage in the middle of the dashboard for a more balanced experience for all passengers.

In both cases, the soundstage is created by strategically delaying audio output from certain speakers, enhancing spatial perception within the cabin.

How TestDevLab evaluates car audio system performance

To accurately assess car audio system performance, a structured testing methodology is essential. While this approach prioritizes technical evaluation over user experience, it provides valuable insights into system performance under controlled conditions. For a more comprehensive understanding of user experience, measurements taken during real driving conditions would be ideal.

This methodology is especially useful during the development phase, helping manufacturers and individuals identify the speaker configurations that deliver the best results for a specific car interior.

• Car under test: Hyundai i30 fastback N, 2020 MY
• Audio system: 4-way speaker system
• Measurement microphone: Dayton EMM-6 (calibration file included)
• Audio card: Audient, EVO
• Measurement software: Open Sound Meter

• Input 1 - Measurement Mic (48V phantom enabled) - Measurement channel
• Input 2 - Pink Noise (from Out 2) - Reference channel
• Output 1 - To car system
• Output 2 - Loopback to In 2

The audio system features four main speakers—one in each door—along with three additional speakers at the front of the cabin and a subwoofer, bringing the total to eight speakers. 

Measurement pre-conditions:

• The microphone calibration file is loaded
• Microphone is set to the desired position
• Pink noise is fed through the car system 
• Delay applied to reference noise signal (to match timing of noise arrival to measurement microphone)
• Both measurement and reference channels have similar volume
• No equalization in the sound system is applied

Our test results

We conducted all measurements from the driver’s perspective to determine which speaker profile delivers results closest to the Harman target curve in the driver’s position.

Measurement details

Measurement number – Mic Placement | Imaging Mode | Speakers Enabled
*The Harman target curve is overlaid on the Open Sound Meter measurement.

Note: Even a slight change in microphone position can affect frequency response measurements. For more precise conclusions, multiple measurement points should be used, and the frequency response should be averaged. Ideally, a stereo microphone with a human-like head and torso would provide the most accurate results.

Below are screenshots of the graphs displaying measurements taken in Open Sound Meter with the Harman curve overlaid:

#1 - Driver seat | Center focus | All speakers

Compared to the Harman curve, we can observe several points in the frequency response that require precise equalization to achieve a more balanced curve. These include reductions at approximately 60 Hz, 100 Hz, 250 Hz, 3.6 kHz, 7 kHz, 9 kHz, and 13 kHz, as well as an overall volume decrease in the low-end region by about 10 to 20 decibels.

#2 - Driver seat | Center focus | Front speakers

A similar situation occurs when only the front speakers are enabled for measurement.

#3 - Driver seat | Driver focus | All speakers

In this setting, the front left speaker is delayed to sync with the right speaker, enhancing stereo imaging for the driver. The "Driver Focus" setting further increases the difference between low-end and mid/high frequencies.

#4 - Driver seat | Front passenger | All speakers

We've added this additional measurement to enhance the front seat passenger's experience. 

Test results summary

The audio measurements provide valuable insights into the performance of the car’s stock audio system compared to the Harman curve, widely regarded as the industry standard for balanced sound.

The stock settings emphasize low frequencies, catering to bass enthusiasts who prefer a stronger, more powerful low-end response. However, analysis reveals specific frequency ranges that could benefit from equalization adjustments. Fine-tuning these frequencies would create a more balanced sound profile, bringing it closer to the Harman curve while improving clarity and overall audio quality.

Activating the driver focus setting helps balance low and high frequencies more effectively, enhancing the listening experience for the driver by delivering a more even distribution of bass, midrange, and treble. However, some frequency imbalances remain.

For more precise and comprehensive measurements, future tests should incorporate a head and torso simulator along with multiple measurement points throughout the cabin. Averaging results from different positions would offer a more realistic representation of how passengers experience the sound, providing deeper insights for both technical evaluation and user experience improvements.

Final thoughts

Recent years have shown a steady increase in customer interest in premium car audio. Advances in digital signal processing, surround sound, and high-resolution audio are reshaping customer expectations, and driving innovation in in-car audio experiences. However, emerging technologies like machine learning and artificial intelligence could further enhance audio system performance and efficiency while also making premium sound more accessible. These advancements would enable systems to better adapt to and cancel a wider range of noise frequencies and patterns, providing passengers with a quieter and more immersive listening experience.

Our testing results highlight the technical range of speakers and their performance within specific car interiors. By analyzing frequency response, we can assess how different settings impact the listening experience and how closely a car's audio setup aligns with the Harman target curve—considered optimal for in-car audio. This helps determine the most effective DSP settings for improving user experience and evaluating overall audio imaging.

Looking ahead, these measurements could aid in comparing different speaker systems within a car environment, identifying the best fit for a given interior, and assessing the impact of Passive Noise Cancellation (PNC) and Active Noise Cancellation (ANC) on audio quality. Additionally, they provide insight into how noise levels while driving affect listeners' audio perception.

Achieve the perfect balance between immersive sound quality and noise reduction. Whether you're an automaker, audio engineer, or enthusiast looking to fine-tune your car’s sound system, comprehensive testing is key to optimizing performance. Reach out to learn more about our audio testing services!