REFERENCE

PODJETJA

  • FNT (Force Network Technology) Supernal Hyundai
  • DAIMLER – Mercedes Benz (Germany)
  • CORSAIR (USA)
  • AUVA & Fellner GmbH- Allgemeine UnfallVersicherungAnstalt (AUT)
  • NORSONIC (Norway)
  • ZUS d.o.o. (CRO)
  • Industrija Apna Kresnice
  • BSH
  • DOMEL
  • GORENJE
  • HYDRIA
  • PORT OF KOPER, IntraLighting, AKRAPOVIČ, MSX, YDRIA MOTORS,
  • TRIMO TREBNJE, PETRIČ d.o.o., ISKRA EMECO, Elpro Križnič,
  • COURT EXPERTISE – Analysis of the spread of low-frequency noise in the city center
  • RESEARCH PROJECT: MOPE – Wind turbine Noise
  • Biodiversity

UPORABA AKUSTIČNE KAMERE

  • Cementarna Split Sv. Kajo
  • Rafinerija Pančevo
  • Cementarna Split Sv.Juraj
  • Termo elektrarna Brestanica
  • Luka Koper
  • LEK Verovškova
  • LEK Prevalje
  • URSA Novo Mesto
  • NIKO Železniki
  • IGM Zagorje
  • LESONIT Ilirska Bistrica
  • Termoelektrarna Šoštanj
  • TPV Jesenice
  • BSH
  • Fakulteta za Strojništvo Maribor
  • ISKRA Mehanizmi
  • DOMEL Železniki

projekti

Psychoacoustics of breaking noise
Merceds Benz (Germany)

R&D project (2019 – 2022) was performed for the company DAIMLER Benz under the cooperation with Institute for automotive engineering at Technical University Graz. Creep Groan noise has been investigated with the purpose to evaluate its noise annoyance and simultaneously to develop an algorithm for its detection in real time. Multichannel adaptive FIR filters have been implemented to identify transfer path from vibrations on the breaks to noise in the cabin. Psychoacoustic model based on subjective test has been developed based on psychoacoustic features; Loudness, Roughness and Tonality.

Artificial intelligence (Self learning, unsupervised classification)
K-Means and SOM

Practical results: A model for calculation of noise annoyance directly from vibration signal has been developed in order to predict noise in the development stage of the breaks. Real time algorithm has been devised as a sensor for detection and classification of creep groan, with the purpose to control the braking system to avoid unstable operating conditions.

System for Automatic Noise Source Identification and Classification
Norsonic (Norway)

SANSIC: A consortium of NORSONIC sales representatives sponsored the R&D project (2012-2022). Participating companies have a lot of experience in environmental noise measurement. These measurements are still being approached individually. So far, automation of noise measurement has been considered impossible. With the introduction of a system for dominant noise source direction sensing, based on beamforming, and a newly introduced physical quantity “immission directivity”, a possibility of measurement automation emerged. Immission directivity enables the classification of sound events in a much easier way since the three components are added to the vector of sound signal features: 1. direction of the dominant source, 2. the speed of a moving dominant source, and 3. the dominant noise source level, which can be directly compared with the level of background noise. In addition, beamforming improves the signal-to-noise ratio of the recorded dominant sound, thereby increasing credibility of the classification process.

Practical result: A granted patent and prototypes of the system operating in Germany, Switzerland, Slovenia and Croatia.

Scientific contribution: Introducing a completely new insight into the measurement of noise in the environment, based on the newly defined quantity “immission directivity”.

Dedicated Acoustic Camera
 ZUS (CRO)

R&D project (2016-2020) for ZUS d.o.o., Croatia, Osijek. ZUS deals with acoustic engineering and needed an acoustic camera to analyze different noise sources. They were looking for a modular design of acoustic camera which would allow them a simultaneous work in the near field and in the far field. In addition, they wanted to combine the video with an acoustic movie in order to monitor moving noise sources and to track aircraft noise. We developed, designed and build acoustic camera for their dedicated type of use, (Picture on the left). This design was the cue for another project, for monitoring airplanes and drones (Picture on the right)

Practical result: Acoustic camera with modular system that enables automatic switching between measurements in the near and far field.

Scientific contribution: Algorithm for automatic recognition of the near and far field noise.

Industrija apna Krsnice  (SLO)

Blender, BSH(SLO)

R&D project 2022: Blender cooling fan noise control
Depending on the measurements of pressure drops, flows and sound level, we come to the following conclusions:

  • By optimising the spiral and outlet grilles, the flow rate was increased from 13 l/s to 16 l/s.
  • By using a different spiral (a smaller „tongue” and expanding without additional obstacles) and reducing the area of the outlet grilles, we noticeably reduced aerodynamic noise at the exit of the prototype; 2 dBA or 3 dB(lin))
  • The type of the of the electric motor control affects the overall noise level.
  • Depending on the vibration of the wall at some operating points,
    noise could be slightly reduced by wall reinforcements.
  • Optimization of the fan spiral and output grid is required for major improvements in device noise.
  • Characteristic is improved by using the flow vanes (flow guides) at the rotor inlet.
  • Improvements are possible using the appropriate rotor geometry with more rearward-twisted blades.

Noise Control of centrifugal blower
Domel (SLO)

R&D project (2014 – 2018) was performed for the company DOMEL d.o.o. which has over 20% of the world market share for centrifugal blowers used in vacuum cleaners. Their aerodynamic performance is well-optimized nowadays, but the same does not apply to their acoustic performance. Noise control studies of centrifugal fans are often focused on designed operating conditions or operating conditions close to the onset of instability. This R&D project was focused on the development of an alternative geometry for the centrifugal impeller which would improve noise control in a wide range of operating conditions. In this R&D project, the term noise control referred to noise level reduction and additionally to manipulating the psychoacoustic properties of noise.

Practical results: Geometry of the centrifugal impeller presented in Figure 1. Impellers with a triangular flow channel achieve an aerodynamic performance which is comparable to that of standard impellers. The results also show that impellers with inclined blades deliver superior results in psychoacoustic metrics compared to impellers with upright blades.

Laundry dryer noise control
Gorenje (SLO)

Laundry dryer noise control: The purpose of this ongoing R&D project (2019-2022) for company GORENJE d.d. is to identify dominant noise sources, and to adopt appropriate and financially acceptable noise control measures, prior the onset of production. Identification of vibro-acoustic properties of the laundry dryer includes all active elements in the system as well as an integral  analysis of the system as whole.

•First results are very encouraging, while we already managed to reduce noise for more then 3 dB, during the whole drying cycle, as shown in figure below.

Tumbling Metering Pump – Inverse engineering
KOLEKTOR (SLO)

Inverse engineering: Tumbling metering pump is intended for small flow rates up to 10 l/min and for pressure up to 10 bar. The main purpose of the study was to identify the most influential parameters for ensuring the quality of production. Oscillations of the rotor in axial direction were identified to be the dominant source of pump characteristics deviation. Identification was based on analysis of sound and vibration signals.

Practical results: Identification of the main problem for achieving continuous production quality. It turned out that precision of pump rotor and stator manufacturing is not as significant as axial force oscillations of the pump rotor on the pump characteristic. Consequently the research was focused away from providing precision of parts towards the geometry of the electric motor rotor, responsible for providing axial force.