# SIDLAB Software & Hardware

##### SIDLAB – Software Suite for Muffler and Silencer Design

SIDLAB Suite is a combination of software and hardware solutions for the analysis and measurement of sound generation and propagation inside duct networks. This can be applied to Intake and Exhaust systems, Power generation, Oil & Gas pipe networks and HVAC systems. It offers a complete characterization of the system, including both simulation and validation measurements. SIDLAB Acoustics and SIDLAB Flow design the system to have a good acoustic performance keeping the pressure drop low enough. The results are then validated using SIDLAB Measurement or SIDLAB Acquisition in the SIDLAB Measurement Rig.

SIDLAB Optimization and Parameterization tools offer larger possibilities for an efficient design. SIDLAB calculations are done in MATLAB, and the source code is offered. This is a good advantage for advanced users to perform their custom analysis. Calculation time is typically a few seconds on a normal PC. Post-processing within SIDLAB is simple and straightforward, with the possibility to save the results in different formats. SIDLAB compiles a long experience and know-how of accurate modeling for all types of duct acoustic applications in research, teaching and consulting.

##### SIDLAB – Acoustics

This module models the generation and propagation of low-frequency sound in complex duct networks. The frequency range is limited to the plane wave region in the connecting pipes. It is based on linear acoustic theory and all elements, e.g., a complex muffler, are reduced to two ports while terminations and sources are represented as one-ports. A number of standard elements representing common duct and pipe elements as well as basic muffler types are available as building blocks, which can be connected to form a network. All standard element models are validated and are based on the best and most recent models published in the literature. The users have the possibility to add their own elements as user-defined elements.

##### SIDLAB Acoustics calculates:

- Transmission Loss and Insertion Loss in dB
- Noise Reduction in dB, narrow band, octave and third octave.
- System Resonances
- The elements of the Transfer and Scattering Matrices for each element and for the full network.
- Sound Pressure RMS and phase at each node in the network. (Pa or dB, narrowband, octave and third octave).
- Sound Power exchange to and from the network at each node. (W or dB, narrowband, octave and third octave).
- Sound Pressure RMS outside the network at a predefined receiver position. (Pa or dB, narrowband, octave and third octave).
- Transfer Function between any two nodes in the network.

##### SIDLAB Acoustic capabilities

- Work with different unit systems to define the dimensions of the network: m, mm and inch.
- Save different versions of the design in the same project.
- The fluid medium can be a perfect gas or a liquid. Available editable library of common fluids.
- Element Manager: Add new elements, delete elements, and modify their list of properties.
- The system network can be drawn in 2D or 3D with a variety of drawing and editing tools.
- Drawing the network in 3D has no influence on the calculation. 3D Networks are only for visualization purposes.
- Several convenient ways to manipulate the results and export them in different formats.

##### SIDLAB Acoustics special calculations

- Engine order vs. Engine RPM calculation: The frequency vector is calculated automatically. Extra needed input data is the inlet flow and temperature at each RPM.
- Optimization: Optimize the system performance (TL – IL – radiate pressure) for a range of frequencies using any number of variables. Define equality and non-equality dimensional constraints. Possible to include the allowable pressure drop as a constraint.
- Parameterization: Choose a single parameter inside the network, perform a parametric analysis by varying the value of this parameter within a specified range with a specified step. The results are shown for all values of the parameter simultaneously.

##### SIDLAB – Flow

This module is an add-on SIDLAB Acoustics. This is a very quick 1D tool to calculate the pressure drop introduced by the designed muffler system. It calculates the flow distribution and pressure drop inside the network using a two-port formulation, and feeds the results into the acoustic calculation in SIDLAB Acoustics. The acoustic performance of some elements like perforates is very dependent on the amount of flow inside the element. SIDLAB Flow uses the same network built in SIDLAB Acoustics.

##### SIDLAB Flow calculates:

- Flow distribution: how much flow in kg/s is going through each element.
- Pressure drop across each element in the network for the given inlet mass flow.
- Flow Mach numbers in each element.
- Flow – pressure drop curve for the system.

##### The flow can be introduced into the network in two ways:

- A prescribed flow source at one inlet of the network. Inlet flow can be defined as:
- Mass flow in kg/s
- Flow velocity in m/s
- Flow Mach number

- Several external static pressure sources connected to different inlets/outlets in the network.

##### SIDLAB – Acquisition

SIDLAB Acquisition is used to acquire the measurement data needed to characterize the passive acoustic properties (e.g. Transmission Loss) of two-port elements (e.g. exhaust or intake mufflers). SIDLAB Acquisition is provided together with a Data Acquisition System and the measurement microphones.

It automates the measurement procedures accounting for different theoretical and practical considerations. Different excitations (random or stepped sine) can be used. The results are stored in different formats compatible to SIDLAB Acoustics and can be used to simulate a complete system. SIDLAB Acquisition is very useful for companies and research institutes, who perform this measurement as a standard measurement which is repeated frequently throughout the design process. SIDLAB Acquisition uses the two-source location technique which has been proven to be the most stable and most efficient technique to measure transmission loss.

SIDLAB Acquisition interface guides the user through the measurement procedure:

- Properly connect the cables
- Set the rig dimensions
- Perform the absolute and/or relative calibration
- Conduct the upstream and downstream measurements
- Calculate the transmission loss and the transfer matrix for the measured object
- Optional add-on: Measure the pressure drop across the muffler at different flow speeds and calculate the muffler loss coefficients
- Optional add-on: Measure the flow generated noise inside the muffler (radiated sound power

SIDLAB Acquisition has the following advantages over other Data Acquisition systems:

It supports stepped sine capabilities which provide better results, especially with flow. High Signal to Noise Ratio, easier to extract the loudspeaker signal from the flow noise.

It is easier to use and faster to do repeated measurements.

It has all functionalities integrated in one place.

The results that are provided by SIDLAB Acquisition Software are:

- Transmission Loss in downstream (exhaust) and upstream (intake) directions.
- Noise Reduction
- Components of the Transfer and Scattering Matrices
- Acoustic Pressure at all the microphones and the coherence to the reference signal
- Background Noise and Flow Generated Sound Power
- Pressure drop – flow curve, and loss coefficient

The software supports a variety of post-processing functions. It also supports the export of the raw data for further post-processing in another software. Different versions of the measurement can be saved in one project file with several functionalities to compare with other versions in other project files.

##### SIDLAB – Measurement Rig

Mufflers are widely used to reduce the exhaust and intake noise for different applications. Every muffler has to be tailored carefully to the engine to which it is connected. One very important tool of muffler design is the measurement of its properties, acoustic performance, and pressure drop.

The introduction of flow is a key issue as it simulates a real engine situation. The two-source technique has been proven to be the most stable and most efficient technique to characterize the full scattering matrix of the muffler. At several companies and research institutes, this has become a standard measurement which is repeated frequently throughout the design process. This is a new platform to measure the passive (e.g. Transmission Loss) and active (flow-generated noise) properties of mufflers.

Stepped sine excitation is used with simultaneous excitations from both sides of the muffler. The stepped sine excitation is optimized to reduce the needed time without jeopardizing the quality of the measurement.

Measurement of flow background noise, microphone coherence, and pressure drop are also performed.

This platform is based on a combined JAVA/NI software and National Instruments Data Acquisition cards, to automate the measurement accounting for different theoretical and practical considerations.

Our solution for the measurement of muffler acoustic performance includes the following standard components:

- SIDLAB Measurement Rig
- SIDLAB Acquisition Software
- SIDLAB Data Acquisition System
- SIDLAB Flow Measurement Kit
- Acoustic Sensors
- Commissioning: Installation and training

**Figure 1** Real view of the two-port test rig, showing the test object, microphones, loudspeakers, and end mufflers