Delay-and-Sum-Beamforming is the most widely known sound localization technique. It is based on the following principle: the sound of different point sources require different amounts of time to reach the array microphones (Fig.1). By calculating the time differences between a sound event and each microphone of an array, direction and strength of sound sources are determined. The calculated sound pressure is then mapped on the optical picture of the measurement object using NoiseImage. We offer different modules for 2D photos and 3D photos or movies! This way, sound emissions can be analyzed within their context of origin and with high regard to reality. The implemented algorithms also take the most important psychoacoustic parameters like loudness, sharpness and roughness into account.
Delay-And-Sum-Beamforming in the Frequency Domain allows acoustic evaluation via the frequency domain. In acoustics, periodic time signals are described by their spectra in the frequency domain. Spectrum and spectrogram show the different frequencies a signal is composed of. To break down the continuous, aperiodic signals into a continuous spectrum, the Fourier Transformation needs to be applied. By transforming the signals, a transition from time to frequency domain is possible and the spectrum and spectrogram can be calculated in NoiseImage.
The resulting acoustic photos and videos in 2D and 3D provide a powerful tool for sound analysis, noise reduction, and quality management.
Depending on the beamforming application, different microphone arrays, varying in size, geometry, and number of microphones are used.
Fig 1: The Localization Principle
Fig. 2: Different spectrograms and maps - Measurement of a sewing machine
This type is suitable for various 2D applications - inside and outside. Depending on the measurement scenario, an array can be comprised of 32 microphone channels, e.g. for measurements in acoustic labs, up to 72 microphone channels, e.g. for free field measurements or large objects.
This microphone array is the best choice for measurement objects that are farther away (~7 - 300 m).
Specifically developed for interior measurements, these arrays are used for 3D applications: The spherical arrays receive signals from all directions. The sound field is then mapped onto 3D models.
To build your own array for your individual measurement scenario, you can use our Design Kit with ADECO Software or the 3-in-1 Array.
Acoustic holography is a technique for determining the radiating structural acoustic behavior of surfaces by measuring in the acoustic nearfield. A complex 2D measurement of the acoustic field is made in the domain of evanescent wave behavior. Using a wavenumber-domain Fourier Transform and applying wave propagation theory results in a complete description of the structure's acoustic field in three dimensions, yielding computations of sound pressure, particle velocity, and sound intensity. A variety of algorithms exist for establishing the acoustic hologram, including the Statistically Optimized Nearfield Acoustic Holography (SONAH) and the Helmholtz Equation Least Squares (HELS) method.