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Sound

Department 1.6

Scientific News from the Department

Erweiterung des Frequenzbereiches des PTB-Schallnormals bis herunter zu 2 Hz für die Rückführung akustischer Messungen im Infraschallbereich

Die Primärkalibrierung in der Druckkammer liefert das zurzeit präziseste Verfahren zur Darstellung der Schalldruckeinheit. Um diese mit höchstmöglicher Genauigkeit zu realisieren, bedient man sich des Reziprozitätsverfahrens zur Kalibrierung von hochstabilen genormten Kondensator-Mikrofonen, den sogenannten Laboratoriums-Normalmikrofonen. Sie zeichnen sich dadurch aus, dass sie einen großen... - more...

Robust membrane hydrophone for the measurement of high-intensity therapeutic ultrasonic fields

Exceptionally robust piezoelectric membrane hydrophones for measurement of extreme acoustic pressure waveforms were developed until ready for marketing in Working Group 1.62 Ultrasonics of PTB in cooperation with the Gesellschaft für Angewandte Medizinische Physik und Technik (GAMPT) mbH, Merseburg. - more...

PTB-Kalibrierservice für Luftultraschall

Bisher gab es für Messungen von Schall mit Frequenzen über 20 kHz noch keine metrologische Rückführung für die Schalldruckeinheit Pascal. An der PTB wurde nun ein Verfahren zur Kalibrierung von Mikrofonen im Ultraschallbereich bis zu 100 kHz entwickelt. Damit können Bezugs- und Gebrauchsnormale für Labore aus Industrie und Forschung hergestellt werden, um eine Rückführung für Luftultraschall zu... - more...

Neue Bezugshörschwellen zur Anwendung mit einem Ohrsimulator für Neugeborene

Da Neugeborene und Kleinkinder erst bei ziemlich lauten Schallereignissen eine Reaktion zeigen, die eine Hörempfindung beweist, werden bei Ihnen zur Gehörprüfung objektive Audiometrieverfahren, wie z. B. die Messung der durch akustische Stimuli ausgelösten Hirnströme, eingesetzt. Die Schallreize (Stimuli) werden dabei über Einsteckhörer wiedergegeben. Die dafür erforderlichen... - more...

Assessment of airborne ultrasound noise

Noise by airborne ultrasound is increasingly polluting our daily environment and can be a risk to our health. There is a growing need for an understanding of the perception and the influence of ultrasound and for establishing consistent regulations. The EARS project has brought researchers of several disciplines together and combined neuroimaging and audiological measurements to create a basis for the assessment of ultrasound noise... - more...

Significance of the results from the EARS project on wind turbines

In our environment and at the workplace, technical sources produce low frequency sound, which is normally considered inaudible. Installations for the production of green energy are among those sources, namely wind turbines producing infrasound. - more...

Thermochromic foils as a simple and magnetic resonance imaging (MRI) compatible way of recording ultrasound-induced heating

Ultrasound is used in medicine for several therapeutic purposes - besides other applications, ultrasound can be used to selectively and locally heat tissue, for example in order to destroy tumors by overheating them. The two most common methods for determining this increase in temperature are either not traceable and provide a poor temporal and spatial resolution (measurements with magnetic...  - more...

Are infrasound and ultrasound audible?

Noise is one of the fundamental environmental factors impairing health and well-being. Whereas in the hearing frequency range, the handling of noise is well grounded and regulated, in the infrasound and ultrasound range, not only the understanding of perception is missing but also fundamental requirements for measuring instruments as well as applicable, practice-related measurement instructions.  - more...

Better accessibility for the hearing-impaired in public transport areas by optimizing public address announcements

The transmission quality of public address systems is evaluated by means of the Speech Transmission Index (STI) that essentially describes the goodness of modulation transfer (DIN EN 60628-16). An STI value of 0 corresponds to a total loss of signal modulation, whereas an STI value of 1 represents ideal signal transmission. For emergency warning systems an STI value ≥ 0.5 is required, which... - more...

Sound source for the objective investigation of the auditory perception of infrasound by means of magnetoencephalography (MEG) and magnetic resonance imaging (MRI)

Contrary to general opinion, the hearing of infrasound (f < 16 Hz) is possible and leads to distress which differs from person to person. However, the mechanisms of this auditory perception by human beings are still largely unexplained. Within the scope of the European research project "EARS", these mechanisms are to be investigated in detail by means of objective procedures of medical... - more...

Directivity pattern of airborne ultrasonic sources

Airborne ultrasound can be emitted with a very strong directivity by sound sources such as ultrasonic cleaning baths or welding equipment. Due to this focusing, very high and hearing-damaging sound pressure levels may occur locally. A new measuring arrangement now allows the emissivity of various sound sources to be determined with high resolution and with level accuracy. - more...

Causes of cell damage in connection with cataract surgery

After cataract surgery, damage to endothelial cells located on the internal side of the cornea is observed in the majority of patients. The causes of this cell damage have not yet been fully clarified; this can affect the corneal dehydration for which these cells are responsible. The – in this case – reduced performance of the endothelial cells leads to a temporary swelling of the cornea in the... - more...

Small sources, loud noise

Ultrasonic equipment, such as, e.g., ultrasonic cleaning baths, can cause very loud noise. High-frequency airborne ultrasound was measured up to 100 kHz on a solid metrological basis for the first time, and different assessment quantities were determined quantitatively. - more...

A sensor to determine the effectivity of ultrasonic cleaning devices

Ultrasonic baths have long been widely used in industry and trade. Despite this, no uniform procedure has existed so far to compare the cleaning results obtained by different devices or the cleaning effectivity of a device in various operating modes. PTB has developed a procedure which allows the abrasion of particles from a surface – hence a cleaning process – to be measured directly. - more...

New procedure for the testing of exponential sweep signals with the aid of Hilbert transform

Acoustic signals are analyzed with the aid of sound level meters, using so-called filter banks. These must be investigated with respect to their real-time capability. For this purpose, test signals are used which must in turn fulfill specific conditions. A new procedure for the testing of test signals for the real-time testing of filters can help to avoid incorrect test results. - more...

Improved damping of acoustic room modes by tunable Helmholtz resonators

In certain frequency ranges, disturbing sound waves cannot be damped with conventional absorbers. An optimization procedure and the use of finely tuned resonators, which are correspondingly dimensioned and positioned in the room, allow different damping effects to be achieved. - more...