Pinpointing Sound: Smart Noise Reduction for Machinery Components
Noise Emissions Under Scrutiny: What Component Suppliers Need to Know
From spindle drives to electric motors and compressors, modern machinery components are expected to deliver not just performance—but also quiet, low-emission operation. As system integrators and OEMs aim to meet tougher regulations and rising customer expectations, suppliers are increasingly being held accountable for the acoustic performance of their components.
Meeting these demands requires more than traditional sound testing. It calls for precise, efficient, and visual tools that can quickly identify and help eliminate unwanted noise emissions—right from the development phase.
This article explores how acoustic cameras support engineers in tackling noise issues early and effectively. We’ll cover how the technology works, its benefits for product development, and walk through three real-world use cases—from quality control of spindle drives to surface noise reduction in electric drives and noise localization in miniature compressors.
What is an Acoustic Camera?
An acoustic camera combines advanced microphone arrays with visual technologies to make noise sources visible. It generates acoustic heatmaps that accurately depict the position and intensity of noise sources, enabling quick analysis.
The Seven Bel Sound Scanner is the first acoustic camera based on the Sound Field Scanning principle. It locates sound sources within a frequency range of 125Hz to 44kHz, providing high-resolution acoustic images directly on a mobile device for analysis.
Key Benefits of an Acoustic Camera:
- Precision: Pinpoint location of noise sources by visual representation of hotspots. Even complex noise issues can be efficiently analyzed and resolved.
- Efficiency: Rapid data collection and automated analysis save time and reduce costs compared to manual measurements using single microphones or accelerometers.
- Flexibility: Suitable for a wide range of applications—from small components to large machinery, from cabin measurements to outdoor noise mapping around the machine. Its mobility allowss flexible adaptation to different requirements.
Applications in the Machinery Component Industry
1. Quality Control of Spindle Drives
In industries where precision, reliability, and smooth operation are essential—such as CNC machining or automation systems—the spindle drive plays a critical role. Even small deviations in mechanical behavior can result in unwanted noise, wear, or performance issues. Acoustic cameras allow engineers to detect and localize the exact source of sound emissions in dynamic, fast-moving components like the spindle nut, which may otherwise be difficult to isolate using traditional sensors.
Challenge:
During end-of-line testing, a spindle drive emits audible noise as the spindle nut moves rapidly from one side to the other. Standard measurements confirm that the overall sound pressure level is elevated, but cannot pinpoint whether the source is mechanical (e.g., play in the nut), due to a mounting issue or coming from mechanical excitations of the test rig. The noise is highly transient, making it impossible to analyze the location with microphones or accelerometers alone.
Solution:
Acoustic cameras identify key noise sources in a machinery component. Combined with an understanding of the component’s design and the components it interacts with, engineers and production technicians can quickly and effectively determine the cause of noise levels and implement high-quality technical solutions.
Example:
An acoustic camera is used to visualize the sound emissions during the nut’s high-speed movement from the right to the left. The measurement clearly shows the dominant noise emission originating from the right side of the spindle nut, indicating excessive play or vibration in that area. This targeted insight enables quality engineers to inspect and adjust that specific section—for instance, correcting torque on a bearing preload or re-checking component tolerances—without having to disassemble the full unit.
2. Targeted Noise Reduction in Electric Drives
Electric drives are central to many modern machines and vehicles, offering high efficiency, compact size, and low maintenance. However, as noise regulations tighten and customer expectations for quieter systems rise, minimizing surface noise emissions becomes a key focus in product development. While electric drives are generally quieter than combustion-based systems, they can still generate high-frequency tonal noise from electromagnetic forces or structural resonances. Acoustic cameras provide a fast and effective way to identify these noise sources on the housing or frame—and guide engineers in applying damping materials where they will have the greatest effect.
Challenge:
A common approach to reducing structure-borne noise in electric drives is to apply polyurethane (PU) absorbing material to the housing. However, this introduces a tradeoff: while PU can dampen acoustic emissions, applying the material across large areas can be thermally problematic. That’s why it’s crucial to identify the precise zones of maximum sound radiation, so that acoustic treatment can be targeted only where it’s most effective, avoiding unnecessary coverage and thermal impact.
Solution:
By using an acoustic camera during bench testing of the drive, engineers can visualize sound emission patterns in real time across the entire surface of the unit. The camera highlights localized “hot spots” of acoustic energy. Based on this data, small patches of PU damping material are strategically applied only to the most active areas.
Example:
Acoustic camera measurements show that the majority of the sound radiation comes from an already ribbed section of the housing (left). The engineering team applied a PU strip only to that area, resulting in a 6 dB noise reduction, with no measurable rise in housing temperature (right). The solution was proven to be effective and the production of the molds for the PU absorber could be started without further risks.
3. Sound Emissions from Small Compressors
In appliances like refrigerators, low-noise operation is a critical quality factor—especially for consumer products used in homes, offices, or hotel rooms. While the compressor is the primary noise source in these systems, the actual sound experienced by the user often originates from other components. Vibrations from the compressor can excite nearby structures—such as refrigerant pipes, sheet metal panels, or plastic housings—turning them into secondary but dominant noise emitters. To meet strict acoustic targets and maintain a high-quality user experience, it’s essential to not only test the compressor itself but also understand how its vibrations propagate through the entire system.
Challenge:
In this use case, the source of excitation (the compressor) is known, but engineers observed unexpected noise during testing of a fully assembled refrigerator. Microphone measurements confirmed the presence of elevated sound levels, but could not reliably pinpoint which part of the system was radiating the noise.
Solution:
An acoustic camera is used to visualize sound emissions from the entire refrigerator during compressor operation. The high-resolution sound map reveals noise sources, such as a vibrating section of refrigerant piping.
Example:
During acoustic testing of a new refrigerator model, noticeable broadband medium frequency noise hum was detected—a frequency typical of flow noise. Using the acoustic camera, the team discovered that a copper pipe was emitting that sound. A simple change in the pipe’s mounting bracket—adding a rubber isolator—reduced overall noise levels by 5 dB. The compressor design remained untouched, and the solution added no significant cost or assembly complexity.
Learn More
An acoustic camera is a modern and effective tool for tackling complex challenges in the development and quality control of machinery components. It not only helps find the root cause of acoustic issues unamigously but also supports to ensure compliance with quality control targets.
Your next step: Contact us and discover how the acoustic camera can revolutionize your daily work as a development engineer, production technician, or service technician!