Under regulations such as the EU Machinery Noise Directive, more and more products—from toys and power tools to IT equipment—are required to declare their sound power level on labels and in documentation, rather than simply claiming they are “quiet enough.”

For typical office devices like notebook computers, idle noise is often around 30 dB(A), while full-load operation can approach 40 dB(A). These figures are usually obtained from sound power measurements performed in accordance with ISO 3744 and related standards.

Sound Pressure vs. Sound Power

A noise source emits sound power, while what we measure with a microphone is sound pressure.

Sound pressure varies with room size, reverberation, and microphone distance, whereas sound power is the source’s own “noise energy” and does not change with installation or environment. That makes sound power a better metric for external product noise specification.

In simple terms:

• Sound power is the cause – the energy emitted by the source (unit: W / dB);
• Sound pressure is the effect – the sound pressure level we hear and measure (unit: Pa / dB).

ISO 3744 defines how to do this in an “essentially free field over a reflecting plane”: arrange microphones around the source on an enveloping measurement surface, measure the sound pressure levels on that surface, then apply specified corrections and calculations to obtain stable, comparable sound power levels.

Device Under Test: An Everyday Notebook Computer

Assume our DUT is a 17-inch office notebook. The goal is to determine its A-weighted sound power level under different operating conditions (idle, office load, full load), in order to:

• Compare different cooling designs and fan control strategies;
• Provide standardized data for product documentation or compliance;
• Supply baseline data for sound quality engineering (for example, whether the fan noise is annoying).

The test environment is a semi-anechoic room with a reflecting floor. The notebook is placed on the reflective plane, and multiple microphone positions are arranged around it (using a hemispherical frame or a regular grid). Overall, the setup satisfies ISO 3744 requirements for the measurement surface and environment.

Measurement System: SonoDAQ Pro + OpenTest Sound Power Module

On the hardware side, we use SonoDAQ Pro together with measurement microphones, arranged around the notebook according to the standard.

OpenTest connects to SonoDAQ via the openDAQ protocol. In the channel setup interface, you select the channels to be used and configure parameters such as sensitivity and sampling rate.

From Standard to Platform: Why Use OpenTest for Sound Power?

OpenTest is CRYSOUND’s next-generation platform for acoustic and vibration testing. It supports three modes—Measure, Analysis, and Sequence—covering both R&D laboratories and repetitive production testing.

For sound power applications, OpenTest implements a sound-pressure-based solution fully compliant with ISO 3744 (engineering method), and also covering ISO 3745 (precision method) and ISO 3746 (survey method). You can flexibly select the test grade according to the test environment and accuracy requirements. The platform includes dedicated sound power report templates that generate standards-compliant reports directly, avoiding repeated manual work in Excel.

On the hardware side, OpenTest connects to multi-brand DAQ devices via openDAQ, ASIO, WASAPI, and NI-DAQmx, enabling unified management of CRYSOUND SonoDAQ, RME, NI and other systems. From a few channels for verification to large microphone arrays, everything can be handled within a single software platform.

Three Steps: Running a Standardized ISO 3744 Sound Power Workflow

Step 1: Parameter Setup and Environment Preparation

After creating a new project in OpenTest:

1. In the channel setup view, select the microphone channels to be used and configure sensitivity, sampling rate, frequency weighting, and other parameters.
2. Switch to Measure > Sound Power and set the measurement parameters:
   • Test method and measurement-surface-related parameters;
   • Microphone position layout;
   • Measurement time;
   • Other parameters corresponding to ISO 3744.

This step effectively turns the standard’s clauses into a reusable OpenTest scenario template.

Step 2: Measure Background Noise First, Then Operating Noise

According to ISO 3744, you must measure sound pressure levels on the same measurement surface with the device switched off and device running, in order to perform background noise corrections.

In OpenTest, this is implemented as two clear operations:

• Acquire background noise
  Click the background-noise acquisition icon in the toolbar. OpenTest records ambient noise for the preset duration.
  • In the survey method, OpenTest updates LAeq for each channel once per second;In the engineering and precision methods, it updates the LAeq of each 1/3-octave band once per second.
• Acquire operating noise
  After background acquisition, click the Test icon. OpenTest will:
  a. Record notebook operating noise for the preset duration;
  b. Update real-time sound pressure levels once per second;
  c. Automatically store the run as a data set for later replay and comparison.

Step 3: From Multiple Measurements to One Standardized Report

After completing multiple operating conditions (for example: idle, typical office work, full-load stress):

• In the data set view, select the records you want to compare and overlay them to observe sound power differences under different conditions;
• In the Data Selector, click the save icon to export the corresponding waveform files and CSV data tables for further processing or archiving;
• Click Report in the toolbar, fill in project and device information, select the data sets to include, adjust charts and tables, and export an Excel report with one click.

The report includes measurement conditions, measurement surface, band or A-weighted sound power levels, background corrections, and other key information. It can be used directly for internal review or regulatory/customer submissions, following the same idea as other standardized sound power reporting solutions.

From a Single Notebook Test to a Reusable Sound Power Platform

Running an ISO 3744 sound power test on a notebook is just one example. More importantly:

• The standardized OpenTest scenario can be cloned for printers, home appliances, power tools, and many other products;
• Multi-channel microphone arrays and SonoDAQ hardware can be reused across projects within the same platform;
• The test workflow and report format are “locked in” by the software, making it easier to hand over, review, and audit across teams.

If you are building or upgrading sound power testing capability, consider using ISO 3744 as the backbone and OpenTest as the platform that links environment, acquisition, analysis, and reporting into a repeatable chain—so each test is clearly traceable and more easily transformed from a one-off experiment into a lasting engineering asset.

Visit www.opentest.com to learn more about OpenTest features and hardware solutions, or contact the CRYSOUND team by filling out the “Get in touch” form below.

In acoustic and vibration testing, engineering teams often find themselves jumping between multiple software tools and data acquisition systems from different vendors. Interfaces vary, workflows are fragmented, and new engineers can spend a significant amount of time just learning the tools before they can focus on the engineering problem itself.

OpenTest, developed by CRYSOUND, is a next-generation acoustic and NVH testing platform designed for engineers, researchers, and manufacturers. Built around the principles of an open ecosystem, AI-driven intelligence, and high compatibility, it allows users to complete the entire workflow—from acquisition to reporting—within a single software environment.

OpenTest supports three operating modes: Measure, Analysis, and Sequence, covering both laboratory validation and repetitive production testing. Core capabilities include real-time monitoring and analysis, FFT and octave analysis, sweep analysis, sound power testing, sound level meter functions, and sound quality analysis. The platform also provides standard test reports and dedicated sound power reports that comply with international standards.

On the hardware side, OpenTest connects to a wide range of multi-brand DAQ devices via mainstream audio protocols such as openDAQ, ASIO, and WASAPI, as well as optional proprietary drivers such as NI-DAQmx, enabling unified management of CRYSOUND SonoDAQ, RME, NI, and other devices within a single platform. On the software side, its modular plugin architecture exposes interfaces for Python, MATLAB, LabVIEW, C++ and more, making it easy for teams to package in-house algorithms and domain applications as plugins and deploy them within the same environment.

From Acquisition to Report: A Three-Step Quick-Start Workflow

1. Installation and Basic Connectivity – Let the Signals In

• Download the latest installer from the official website www.opentest.com and complete the installation.
• Connect your DAQ device to the PC; for your first trial, you can simply use the built-in PC sound card to run a quick test.
• In the OpenTest setup section, scan for available devices and select the devices and channels you want to use. Once added to the project, your basic connectivity is complete.

2. Run Basic Tests with Real-Time Analysis – See It First, Then Optimize

• In the channel management view, select the input/output channels you want to use and configure key parameters such as sensitivity, sampling rate, and gain.
• The system automatically activates the Monitor panel, where you can view real-time waveforms, FFT spectra, and key metrics such as RMS level and THD at a glance.
• When needed, you can enable the built-in signal generator to output excitation signals and use the recording function for long-duration acquisition, preserving data for later comparison and analysis.

3. Perform In-Depth Analysis and Reporting in the Measure Module – Turning Data into Decisions

• Switch to the Measure module to access advanced applications such as FFT analysis, octave analysis, sweep analysis, sound power testing, sound level meter, and sound quality—providing everything you need for deeper investigation.
• Use the data set functionality to review and overlay historical records, so you can compare different samples, operating conditions, or tuning strategies side by side.
• Waveforms and analysis results can be exported at any time. With the reporting function, you can generate test reports with a single click, closing the loop from test execution to final deliverables.

Who Is OpenTest For?

• New acoustic and vibration test engineers who want to establish a complete workflow quickly using a single toolchain.
• Laboratories and corporate teams that need to manage multi-brand hardware and consolidate everything into one unified software platform.
• Project teams in automotive NVH, consumer electronics, and industrial diagnostics that require high channel counts, automation, and AI-enhanced analysis capabilities.

Wherever you are on your testing infrastructure journey, OpenTest lets you start with a free entry-level edition and adopt an open, intelligent, and scalable ecosystem with a low barrier to entry. Visit www.opentest.com to explore detailed features, supported hardware, and licensing and plan options, and book a demo to see how OpenTest and CRYSOUND can help you build an efficient, open, and future-ready acoustic and vibration testing platform.

SonoDAQ is the next-generation high-performance data acquisition system, specifically designed for acoustic and vibration testing. It features a modular architecture, making data acquisition more efficient and precise. From industrial environments to laboratory measurements, SonoDAQ meets the demands of high-precision data acquisition and provides seamless support for multi-channel synchronized data collection.

Modular Design, Flexible to Adapt to Various Applications

SonoDAQ adopts a completely new modular design, allowing for flexible configuration based on different needs. Whether you require a basic 4-channel setup or a large-scale system with hundreds of channels, SonoDAQ can easily accommodate both. You can select modules according to your project requirements and expand the system at any time, avoiding unnecessary costs. This flexibility is particularly well-suited for dynamic and evolving testing environments.

High-Precision Synchronization Ensures the Accuracy of Test Results

In acoustic and vibration testing, data accuracy is crucial. SonoDAQ is equipped with a 32-bit ADC and a sampling rate of up to 204.8 kHz. It ensures time synchronization between channels with a time error of less than 100 ns through PTP (IEEE 1588) and GPS synchronization. This level of synchronization precision allows you to obtain reliable and consistent data results, even in multi-channel, large-scale distributed acquisition systems.

Flexible System Expansion with Multiple Network Topologies

Another highlight of SonoDAQ is its powerful distributed acquisition capability. With various network connection methods like daisy chain and star topology, multiple devices can be easily integrated into the same acquisition system. Leveraging PTP (Precision Time Protocol) and GPS synchronization technology, SonoDAQ ensures nanosecond-level synchronization, providing data consistency across devices, whether for small-scale laboratory tests or large-scale field data collection. You can choose different system topologies based on your specific needs, offering flexibility for complex testing scenarios.

Innovative Structural Design, the Ideal Choice for Field Applications

SonoDAQ’s frame is made using 5000t aluminum extrusion technology combined with carbon fiber-reinforced plastic, offering exceptional sturdiness while significantly reducing the device’s weight. Additionally, SonoDAQ supports PoE power supply and hot-swappable batteries, ensuring efficient operation even in harsh environments and meeting the demands of long-duration continuous acquisition. Whether in the laboratory or on industrial sites, SonoDAQ delivers stable performance.

Extensive Signal Compatibility, Expanding Your Testing Boundaries

SonoDAQ supports a variety of signal inputs, including IEPE sensors, CAN bus, digital I/O, and other interface protocols. This allows it to meet a wide range of testing needs, from vibration monitoring to motor noise analysis. Whether you’re conducting basic data acquisition or advanced signal analysis, SonoDAQ provides the precision and flexibility you require.

Enhance Testing Efficiency, Making Data Acquisition Simpler

With the accompanying OpenTest software, SonoDAQ allows you to monitor and analyze collected signals in real-time. OpenTest offers an intuitive interface and powerful data analysis features, making it easier to process and present test data. Additionally, SonoDAQ supports open protocols like ASIO and OpenDAQ, facilitating integration with other testing tools or software.

SonoDAQ will help streamline your testing process, improve data acquisition efficiency, and provide precise measurements in various complex testing environments. Whether it’s noise testing, vibration analysis, or complex acoustic power measurements, SonoDAQ is your ideal choice. Choose SonoDAQ today and bring revolutionary changes to your testing work!

SonoDAQ is ready to transform your testing process — don’t wait to experience its power. Contact us now! Please fill out the ‘Get in touch’ form below, and we’ll get back to you shortly！