How to Choose the Right AVAS Solution: A Technical Selection Guide

1.Introduction
2.Step 01: Identify Your Target Market-Global Compliance First
3.Step 02: Clarify Your Vehicle Type-Packaging and Propagation
4.Step 03: Define the Sound-Safety Function and Brand Identity
5.Step 04: Select the Integration Architecture
6.Step 05: Select the Speaker or Exciter-Physical Reliability
7.Bestar's Professional Acoustic Solutions 
8.Conclusion

Introduction
At low speeds, the combustion noise that pedestrians used to experience whenever a vehicle was in their view is just not present. This and quietness help to improve urban noise conditions but poses a real safety hazard to ready pedestrians, cyclists and visually impaired road members.
This problem is addressed using Acoustic Vehicle Alerting Systems-AVAS. Such systems produce artificial sound when traveling at low speeds to provide the driver with an audible signal to other road users on the presence of the vehicle and the direction in which the vehicle is traveling. Since the rapid uptake of EVs worldwide since then AVAS has ceased to be a regulatory add-on but a safety system that appears in every battery electric and plug-in hybrid car retailed in major markets.
The appropriate AVAS is not a one-stop-shop procurement solution. It denotes regulatory compliance, mechanical packaging, acoustical engineering, system architecture and brand strategy. A bad choice brings about legal liability, and integrations troubles and a product that incorrectly sounds in the market: it was developed.
This blog can offer a systematic outline of the process of AVAS selection that an OEM engineer and program manager undertakes. The steps are focused on one decision point; targeting market compliance to reliability at component level.

Step 01: Identify Your Target Market — Global Compliance First
The first question is not "what should the sound be" — it is "what does the law require." AVAS regulations differ by region, and the differences matter at the engineering level.
UN R138 governs European/Global markets. It requires AVAS activation during reverse travel and forward travel up to 20 km/h. The sound must change continuously with vehicle speed, giving pedestrians a reliable sense of how fast the vehicle is moving. Minimum sound pressure levels are defined at specific measurement distances and speeds. The regulation also specifies that the sound must contain sufficient frequency content to be detectable in typical urban environments.
FMVSS 141 governs the United States market. The structure is similar to ECE R138 in many respects, but the specific sound level requirements, measurement conditions, and speed thresholds differ. US regulations are enforced by NHTSA, and the test procedures are defined in detail. Compliance testing is mandatory before market entry, and the consequences of a failed test at production stage are severe.
GB/T 37153 is the national standard in China. The GB/T 37153 is currently the largest EV market globally with its own requires its own distinct code of sound pressure, frequency distribution, and behavior with speeds but is generally more in line with the ECE approach.
There are three parameters. First, sound pressure level: each standard establishes minimum levels of the dB(A) at specified vehicle speeds, with common levels being 10 km/h and 20 km/h. The sound is supposed to be loud enough so as to be audible in a realistic city environment and not so loud as to cause noise pollution. Second, frequency content: the sound should have particular frequency contents. Some bands will have pure tones necessary so that they can be detected. Regulations typically do disallow sounds composed of very low or very high frequency although these tend to be harder to localize and detect under actual conditions. Third, changeable pitching with acceleration: the sound should be audibly altered with the change of the vehicle speed. It is through that the pedestrians determine whether a vehicle is moving faster, slower, or coming at them. The sound frequency or nature should be in a gradual, auditory manner and should depend on speed.
The practical implication is straightforward. Your target markets define your minimum technical specification. Build the compliance checklist before selecting any hardware or software components.

Step 02: Clarify Your Vehicle Type — Packaging and Propagation
AVAS hardware must fit inside the vehicle and project sound effectively toward pedestrians. These two requirements interact with each other and with the vehicle's physical structure.
Passenger cars, commercial vehicles, and light urban mobility platforms each present different packaging constraints. A passenger car front bumper has limited space behind the fascia. A light commercial vehicle may have more volume available but also more road noise and wind noise at speed. A compact urban EV may have almost no conventional engine bay at all.
Speaker or exciter placement directly affects sound directivity. AVAS sound must reach the pedestrian zones in front of and beside the vehicle. A speaker mounted too high, too far inboard, or blocked by structural elements will not project sound effectively into the pedestrian zone at street level. The physics of sound propagation at the frequencies used in AVAS — typically 315 Hz to 5 kHz — means that placement affects both level and directional character.
Vehicle structure also determines the type of transducer to be used. The traditional cone speakers need a ported or a sealed enclosure to work well. Exciters, these are devices that do not provide sound by vibration on a panel, but rather, use the existing car body panels as radiating surface. This eliminates the need of a special enclosure which is a high package consideration in space constrained installation.
The major questions to be asked in this phase include: Where can the transducer be attached to the vehicle structure? What panel or enclosure is available? How far acoustically is the transducer located in relation to the pedestrian zone? The responses decide the transducer formats that are useable and those that are not.

Step 03: Define the Sound — Safety Function and Brand Identity
AVAS sound design operates within a compliance boundary. Inside that boundary, there is significant room for creative and brand-driven decisions.
Regulations prohibit certain sound types. Music, voice, and natural sounds unrelated to vehicle behavior are generally not permitted. The sound must be clearly associated with a moving vehicle. It must not be confusable with warning signals used by emergency services. These restrictions are practical safety requirements, not arbitrary limitations.
OEMs have actual decisions to take within the allowed space. Design variables are the harmonic structure of the sound, the tonal nature of the sound and the speed of the variation. A sound constructed on basic frequency with limited overtones has a clear straight forward nature. A multiple-harmonic layered sound is more complex and perceived to be rich. These distinctions are sound ethically and to pedestrians, more and more, to customers who are linking the exterior sound of the car to its brand.
Some manufacturers use AVAS as a deliberate brand touchpoint. The sound conveys a specific character — technological, futuristic, premium, or efficient. This is a legitimate engineering and marketing decision. It does not compromise safety. It simply means that sound design becomes part of the vehicle's overall sensory engineering, not just a compliance checkbox.
The practical advice here is to involve acoustic engineers early in the sound definition process. Define the target sound profile before hardware selection, not after. The transducer and drive electronics must be capable of reproducing the target sound accurately and consistently across the full operating temperature and voltage range.

Step 04: Select the Integration Architecture
AVAS can be implemented as a standalone system or as an embedded function within the vehicle's existing electronic architecture.
A standalone AVAS module contains its own control unit, signal processing, power amplifier, and connection to the vehicle speed signal. It operates independently of other vehicle systems. Installation is straightforward. Integration risk is low. The standalone approach is suitable for vehicles where the electronic architecture is already defined and adding a new function to an existing controller is not practical.
An embedded AVAS architecture runs the signal processing and sound generation algorithm inside the Vehicle Control Unit or another existing ECU. Only the power amplifier and transducer are added as hardware. This approach reduces component count and is preferred in vehicles with a highly integrated electronic architecture. It requires closer collaboration between the AVAS supplier and the vehicle systems team, and it demands that the host ECU has sufficient processing headroom.
Communication protocol selection affects both options. CAN bus is the standard for vehicle-level diagnostics, status reporting, and speed signal distribution. It provides reliable, noise-resistant communication across the vehicle network. LIN bus is used for simpler, lower-bandwidth connections — for example, between a main controller and a satellite amplifier module. Understanding which protocols are available at the intended installation point is necessary before selecting a module architecture.

Step 05: Select the Speaker or Exciter — Physical Reliability
An AVAS transducer lives in the harshest zone of the vehicle. It is mounted in or near the front bumper, exposed to road spray, mud, salt, and temperature extremes. It must perform correctly from the first day of vehicle life to the last.
Acoustic Vehicle Alert System​ transducers have the minimum environmental protection of IP6K9K. This implies total dust rejection and immunity against high pressure and intense temperature water jets that is installed in commercial vehicle wash plants. Other manufacturers add other criteria: salt spray resistance as per ISO 9227, thermal cycling down to below freezing temperatures and up to over 212°F(100°C) and vibration endurance comparable to the vehicle road load measurements.
Of great importance is the acoustic stability throughout the life of vehicle. Materials of speaker cones and surround also wear out. Rubber encasings may rupture in exposed spots of UV. It has paper cones that absorb moisture. Polymer compounds become hard at low temperatures and they become soft at high temperatures. Both of these effects modify the frequency response and maximum output of the speaker. 
The important factors are material choice, UV stabilization, environmental sealing and advanced age verification. 

Bestar's Professional Acoustic Solutions
Bestar designs and manufactures AVAS solutions for global EV programs. The company's product range covers the full system: weatherproof transducers rated for front-of-vehicle installation, integrated amplifier and controller modules, and complete AVAS systems with regulatory-validated sound profiles.
Bestar's engineering team supports customers through market-specific compliance requirements, including UN R138, FMVSS 141, and GB/T 37153. Custom sound development, hardware configuration, and system-level validation support are available across the full program lifecycle — from concept through production.
For OEMs entering new markets or updating existing AVAS configurations, Bestar provides a practical starting point: hardware with proven environmental durability, combined with the acoustic engineering support needed to develop and validate a compliant sound profile.

Conclusion
AVAS selection is a multi-discipline engineering task. It requires compliance knowledge, mechanical packaging analysis, acoustic design capability, electronic system architecture decisions, and component-level reliability engineering. None of these dimensions can be addressed in isolation.
The five-step framework in this guide provides a logical sequence. Start with compliance requirements. Understand your packaging constraints. Define the sound before selecting hardware. Choose the right system architecture for your vehicle platform. Specify transducers with verified environmental durability.
A well-executed AVAS program does more than satisfy a regulatory requirement. It gives the vehicle a consistent, controlled acoustic presence in the pedestrian environment. It protects road users. And it gives the OEM an opportunity to extend brand identity into a new sensory dimension that will matter increasingly as the EV transition continues.
For technical consultation, regulatory compliance support, or product specifications, contact Bestar's acoustic engineering team directly.