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  Consulting    NVH Consulting     Methods/ Tools   
  Binaural Transfer Path Analysis and Synthesis (BTPA/BTPS)
Binaural Transfer Path Analysis and Synthesis - BTPA/BTPS - General Description
Based on the demands of the automobile industry, Binaural Transfer Path Analysis and Synthesis (BTPA and BTPS) have been developed for the prediction of sound quality in vehicles, not only in terms of numbers and graphs, but also for binaural auralization.
It is a powerful modeling tool enabling engineers to identify causative mechanisms for noise transfer by distinguishing between excitation source strengths and the transfer behavior of individual elements.
BTPA is a measurement procedure for characterizing individual vehicle noise paths. The results can be used to create an accurate model for path-related noise heard anywhere inside the vehicle, thus yielding possibilities for troubleshooting and sound design.
BTPS is the process of creating listenable vehicle interior noise data based on a BTPA model or modifications to it. Binaural recording and playback technology is used throughout in order to achieve a realistic sound reproduction.
Depending on the application HEAD acoustics consultants apply different methods:
Coherence method, Operational Path Analysis:
- Analysis of wind and tire noise
- Quick source separation (wind noise, single wheels)
BTPA and BTPS, Standard method (time-domain):
- Application for power train, auxiliaries, door slam, etc.
- Good auralisation, valid results, long-time experience
Examples for Fields of Applications
Powertrain NVH   read more
- BTPA/ BTPS Airborne Sound Transfer
  read more
Structure-Borne Sound Transfer
  read more
- BTPA/ BTPS Synthesis Results
  read more
Hybrid-/ Electric Drive Systems
  read more
Hybrid-/ Electric Drive Systems
  read more
Road Noise   read more
- BTPA/ BTPS for Road Noise
  read more
Synthesis of Door Operating Sounds
  read more
Synthesis of Further Sound Sources/
Accessories   read more
Synthesis of Seat and Steering Wheel
Vibrations   read more
BTPA and BTPS, extended matrix method (time-domain):
- Application for stiffly coupled systems, especially chassis and suspension
- Good auralisation
- Improved consideration of crosstalk between paths
- Additions to established matrix-based TPA methods: auralisation, consideration of mount transfer functions
The method is well known for powertrain noise analysis, including both point coupled   structure- borne and identified   airborne source paths to a receiver location. In recent times, the field of application has been extended to airborne and structure-borne road noise as well as accessory noise (windshield wiper, electric power steering) and door opening/closure sound.
The listenability of BTPS results makes BTPA/BTPS one of the best sound quality (SQ) design tools available for vehicle noise assessment. When BTPS results are combined with the   SoundCar playback environment and the   H3S driving simulation system, this offers potential to complete the equation by allowing the user to experience the sound interactively in the same manner and context as a driver, thus termed a •driver-in-the-loop• experience.
This graph shows the principal setup of a typical transfer path model used in the BTPA/BTPS method. Each   structure- borne noise path (left hand side) consists of the triaxial input signal (e.g. engine mount left x-, y- and z- direction), mount transmissibility function (MT), the point mobility of the car body at the attachment point (AM) and the acoustic transfer function.
The   airborne source paths consist of the microphone input signal and airborne transfer function. Additionally, a correction function, taking the coherence between the microphone signals inside the engine compartment into account, is applied.
BTPA flowchart
Click here for a detailed view
Convolving the input signals with the respective transfer paths, the interior noise contributions of each individual path can be calculated. Furthermore, the complete airborne and structure-borne sound contribution and of course the interior noise can be simulated by summing up the noise shares.
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