Listening with the Eyes: The Acoustic Camera

(f.l.t.r.) Dipl.-Ing. (FH) Dirk Döbler, Dr.-Ing. Gerd Heinz, Swen Tilgner

Dr.-Ing. Gerd Heinz (Spokesperson)
Dipl.-Ing. (FH) Dirk Döbler
Swen Tilgner

Gesellschaft zur Förderung angewandter
Informatik e.V. (GFaI), Berlin

Noise can make you ill. Consequently, vehicle and machine designers have the important task of making equipment as quiet running as possible.
But how can you find exactly where the source of noise is in a machine?

The answer: you have to make the racket visible to the eye. The technical means to do so have been created by Gerd Heinz, Dirk Döbler, and Swen Tilgner at the Society for the Promotion of Applied Computer Sciences (GFaI) in Berlin with the invention of an “Acoustic Camera”. Gerd Heinz is responsible at GFaI for Acoustic Camera applications, Dirk Döbler heads software development, Swen Tilgner heads the department Production, Procurement, and Engineering.

Making sound visible
To eliminate the sources of noise in a technical system, engineers first have to know the volume produced by the individual parts of a machine. This was often a difficult and time-consuming process in the past. The Acoustic Camera, however, provides a way of locating noise emissions easily, rapidly, and accurately and thus determine their sources. It is able to produce “sound images” almost as easily as conventional photos are taken with a digital camera. The spatial spreading of sound is thus rendered visible to the human eye.

The Acoustic Camera consists of several microphones arranged in a special pattern. The sounds they record are fed to a data recorder, converted into digital electronic signals and analyzed by a computer. From the different sound waves produced by the different components of a production machine or a vehicle, the PC instantaneously calculates a detailed sound map.

Film the screech of cylinders
With the sound map a digital camera simultaneously takes a picture of the analyzed object. By superimposing both images, it is possible to directly identify and locate what noise is produced where. By recording and joining together several sound images in rapid succession, it is even possible to produce “sound videos” which engineers can use to analyze sound emissions of moving objects, for example, cylinder piston action in an engine.

The research and development team in Berlin introduced the Acoustic Camera to the market in fall 2001. Most units sold to date are used in the automotive industry. Among other things, automotive engineers are interested in the sound design of a vehicle. In the meantime, the sounds of refrigerators, powertrains, and flatscreens are now being optimized with the help of the Acoustic Camera.