The new G.R.A.S. KB5000 right pinna and the KEMAR simulator

A New Soft Ear

The new G.R.A.S. KB5000 right pinna with anthropometric concha and ear canal for KEMAR is made of soft silicone (35 Shore OO hardness). The external shape of the pinna is identical to that of the standardized KEMAR pinna, but the concha and the canal have been modified so that they closely mimic the properties of a real human ear.

The ear canal has been extended and is an integral part of the pinna that now seals directly against the ear simulator. As with the human ear, the ear canal now has the first and second bend, and the interface with the concha is oval. This shape makes it possible to achieve good fit and sealing with anatomically shaped ear-bud headphones and in-ear hearing protectors. Controlling the insertion depth is easy, leading to better insertion consistency and improved repeatability of measurements.

The outer pinna has the same shape as the standardized pinna, but the flexibility has been improved to better mimic the way the human ear collapses when supra-aural and circumaural earphones are mounted. When measuring the frequency response of these types of headphones, more reliable and repeatable measurements can be achieved because of the improved collapsibility of the pinna. In addition to the traditional push mounting from the outside, the pinna is secured with two screws from the inside of KEMAR’s head. These two screws ensure that the pinna is held firmly in place. Therefore, it seals perfectly against the ear simulator and the head, and it is possible to repeatedly mount and dismount DUTs without compromising the seal.
 
At first sight, there is virtually no difference between the standardized KEMAR pinna and the new G.R.A.S. KB5000 right pinna. Touch will reveal the new pinna to be softer since it is made of soft silicone, allowing it to be pressed against the head, just as with a real ear.

The KEMAR

The ear simulators can be incorporated into a Head-and-Torso Simulator (HATS) such as KEMAR, which lends more realism to in-situ anthropomorphic testing. KEMAR is a model of a human head and torso, and has been extensively used for the last 35 years to study the interaction between the human head and torso and sound fields.

The KEMAR head-and-torso simulator for hearing aid tests, ear- and head- phone tests, and sound quality recordings was developed by Knowles Electronics in 1972 and acquired by G.R.A.S. Sound & Vibration in 2005. It is the origin of all other head-and-torso simulators, and thus, the industry standard for in-situ anthropomorphic testing of all kinds of hearing instruments and head- and earphones. The data has been thoroughly documented in numerous studies, some of which have been collected in the book Manikin Measurement by Mahlon D. Burkhard (February 1978).

Introduced in 2013, the new generation KEMAR is available with and without a mouth simulator and fully backward acoustically compatible with earlier KEMAR models. It meets the requirements of American National Standards Institute (ANSI) S3.36 and International Electrotechnical Commission (IEC) 60318-7. KEMAR and can also be configured with more sizes of standardized pinna simulators and various 0.5” and 0.25” pressure microphones for binaural recordings. KEMAR accommodates for LEMO as well as CCP pre-amplifiers which are all electrically accessible from the connector panel on the back.
 
The new generation KEMAR is available with and without a mouth simulator and fully backwards acoustically compatible with earlier KEMAR models.

G.R.A.S. Sound & Vibration

Distinguished acoustic engineer Gunnar Rasmussen, founded G.R.A.S. Sound & Vibration in 1994, and on his 90th birthday continues to inspire with his extraordinary vision and guiding principles for the Danish measurement microphones specialist. As an engineering student Rasmussen already showed great promise. Shortly after his graduation, he was hired by the Danish audio pioneers Brüel & Kjær. In the 1950s, the company sent Rasmussen to the United States to promote products and manage the after-sales service. The inquisitive microphone specialist also took the opportunity to get acquainted with America’s futuristic technologies and to forge ties with a wide range of industries.

The fast-growing American automotive, aerospace, and consumer industries in the 1950s had a continuous demand for more and better acoustic measurement microphones. Through his intense involvement in several different acoustical measurement projects, Rasmussen realized the microphones available at that time needed some serious improvements. After returning to Denmark, he set out to develop a new generation of microphones, using the most advanced materials and assembly techniques. The outcome was a new, revolutionary, and simple design, which for the past 60 years has been preferred for all types of professional acoustic measurements and has been internationally standardized.

At the age of 67, when most people are heading for retirement, Rasmussen left Brüel & Kjær and founded G.R.A.S. Sound & Vibration. What began as a small family business, run by Rasmussen and his wife Hanna Hertz, quickly grew into a respected and leading manufacturer of measurement microphones, turning many of its founder’s so-far unexploited ideas and inventions into commercial successes. Today, the company offers more than 100 different microphones types, employs 90 people, and has offices or affiliates in approximately 40 countries worldwide.

The couple’s sons, Per Rasmussen and Peter Wulf-Andersen, play key R&D roles at G.R.A.S. Sound & Vibration, while Lars Kjærgaard, who joined the company in 2011, has been serving as CEO since 2014. As Chairman, Rasmussen continues to inspire those around him with his extraordinary vision and guiding principles for the company.

He was appointed as chairman of the ISO committee, made a Fellow of the Acoustical Society of America, and he received the Danish Design Awards for his design of measurement microphones and sound level meters. The famous conductor Leonard Bernstein turned to Rasmussen for help producing a better recording microphone for classical music. Rasmussen earned a CETIM award and the International Electrotechnical Commission (IEC) Award.

In 2008, he was presented with the prestigious Lifetime Achievements in Acoustics award by the European Acoustics Association. However, Gunnar Rasmussen does not dwell much on accolades. On the contrary, he seems to be looking ahead to solve the next problem.
www.gras.dk
 
Acoustic engineer Gunnar Rasmussen, founded G.R.A.S. Sound & Vibration in 1994, and on his 90th birthday continues to be one of the leading Danish measurement microphone specialists.



 
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