Got a question?

Feel free to contact us:

GRAS Sound & Vibration 
Europe & Asia     | Americas 
+45 4422 5253    | +1 330 892 7024


Technical Library

Under this menu, you will find a listing of various technical documentation such as technical notes, application notes, handbooks, white papers and other technical information. Product information, manuals and the GRAS catalog continues to be found under the product specific pages. If you are missing a specific note or white paper, please do not hesitate to contact us.

Technical Notes   Aplication Notes   Handbooks   White Papers   Other Technical Information

147AX Positioning Guide, October 2020

Engine noise reduction (ENR) testing is usually performed under laboratory conditions using the reverse transfer path analysis (TPA) technique, where multiple microphones are placed inside the engine bay. This application note describes GRAS´ approach, using the same microphone positions across platforms. This facilitates gathering consistent data that can be reliably compared across every project for benchmarking. READ MORE >

Smart Speaker Acoustic Measurements, December 2021

Smart speakers are a relatively new class of consumer audio device with unique characteristics that make testing their audio performance difficult. In this application note, we provide an overview of smart speaker acoustic measurements with a focus on frequency response—the most important objective measurement of a device’s audio quality.  READ MORE >


The Importance of Measurement Microphone Venting, November 2021

Did you know that the small hole on your microphone serves a vital role in acquiring data? Proper microphone venting can mean the difference between good actionable data and data corrupted by pressure inequalities between the front and back of the microphone diaphragm. Our new application note explains how and why the vents work and why some microphones are front vented and others rear vented.  READ MORE >


How to Match a Measurement Microphone to a Sound Field, April 2021

Selecting the right measurement microphone for the environment is essential for obtaining accurate, actionable measurement data. Therefore, measurement microphones are designed for use in particular sound fields. Understanding the differences between the microphones can help in selecting the right micro¬phone and avoiding potential measurement errors. READ MORE >


Headphone Electroacoustic Measurements, November 2020

Due to the close coupling of earphones to the ears and the acoustic transmission paths involved, headphone measurements are complicated. Our 26-page application note discusses these challenges, headphones types, measurement standards, headphone acoustics, acoustic test fixtures required for measuring headphones, and the practical aspects of headphone measurements. Objective measurements are also discussed. READ MORE >


Loudspeaker Electroacoustic Measurements, November 2020

Compared to electronic audio test, measuring loudspeakers is complicated. First, to measure sound levels accurately requires precision measurement microphones and supporting electronics, which have a known, stable sensitivity and flat frequency response over the frequency range of interest. Measurements are further complicated by the interaction of the loudspeaker under test with the test environment. READ MORE >


147AX Microphone Vibration Sensitivity, April 2020

The design of the 147AX microphone has been optimized for mounting on surfaces and structures to measure the sound pressure in the surrounding air. But what happens when the microphone is mounted on a vibrating surface? This paper shows that, in most cases, 147AX can be safely mounted on vibrating structures without significant impact to the measurement results. READ MORE >

Engine Bay Measurements: Pressure vs Free-field Microphone, April 2020

Many users are still using free-field microphones for engine bay acoustic measurements. An engine bay is far from a free-field environment, which is why the use of a free-field microphone is not recommended for engine bay measurements. This application note uses a practical case to show the differences in results between using a free-field microphone and a pressure microphone for engine bay testing, and expands on why a pressure microphone is better suited for the application. READ MORE >