DIMsilencer Manual

Foreword

This manual describes how DIMsilencer is used as a separate program for searching for silencers or as a noise calculation program through an installation. Each calculation is also linked to a description of the project and its conditions, responsible designer, and client.

The manual presents step-by-step how the calculation procedure is intended to be carried out. The forms and technical documentation that have been used are presented at the back of this manual.

DIMsilencer has four different functions that are divided between four separate main buttons. The first three buttons are used to search for silencers that satisfy various requirements or comparisons between these properties. The fourth and last button, “Calculation for premises”, calculates from the fan up to and including the premises with the various components involved, apart from straight ducts and bends. These and other components can be created and added as static components.

Open DIMsilencer

DIMsilencer's main window features four function buttons. Under the File tab, users can open previous calculations or searches. Before starting any calculations, it is essential to set the correct units for flows and select the relevant unit for noise level, which is done under settings.

The interface includes buttons for:

• Lw: Seek silencer
• Att.: Seek silencer
• Silencer performance
• Room calculation

A screenshot shows the main window with these buttons and a settings dialog for units.

Lw: Search silencer

Enter known information and search

1. Press the “Lw: Search silencer” button.
2. Indicate the silencer's placement: inlet air, outlet air, or before/after the fan. Location affects noise data. If placed at the fan, saved fan data can be added.
3. Enter noise levels before the silencer, divided into frequency bands. Text can be added to describe the installation context.
4. Check the box to divide noise requirements after the silencer into frequency bands. If unchecked, only weighted requirements are used. Forgetting to enter Lw after the silencer results in a message indicating no silencers met the requirement.
5. Enter the intended air flow and maximum pressure drop. A pressure drop of 0 applies to all pressure drops. Duct speed adjusts with silencer dimensions.
6. Select the duct type (Circular or Rectangular) and silencer type (Straight or Bent) on the right-hand side.
7. Enter the silencer's size.
8. Enter lengths X and Y; the minimum length is 100 mm. For straight silencers, the length can be locked. Standard lengths include 650, 1250, 1850, 2450 mm, and +100 mm for cleanable units.

Tip: Check the speed within the silencer when entering dimensions, as errors are common here, potentially due to incorrect flow or undersized ducts, leading to high self-generated emissions.

9. Press “Search” when all details are correct.

DIMsilencer may indicate that no silencers meet the requirements. If potential silencers are displayed, select “Yes” to view them. If “No” is selected, the user is returned to check entered data, often the Lw requirement after the silencer, as sometimes no suitable silencer exists, requiring a combination of multiple silencers.

The search results show values across frequency bands. Display options (damping, self-generated emissions) can be selected from a scroll list. DIMsilencer displays the selected silencer's technical data, including dimensional diagrams or pictures.

Example: A user might choose a rectangular silencer with a round connection (LRCA-400-500).

The list can include multiple silencers that collectively meet the requirements. Silencers can be removed to perform new searches. Once satisfied, the calculation can be saved and printed, after entering project data.

Att.: Search silencer

Enter known information and search

1. Press the “Search silencer” button.
2. Indicate the silencer's placement (inlet air, outlet air, before/after fan).
3. Enter the required damping, divided into frequency bands.
4. Enter the maximum noise generation to ensure the silencer does not produce more noise than the duct after it. The default is 99.
5. Enter the intended air flow and maximum pressure drop. A pressure drop of 0 searches all pressure drops. Duct speed changes with silencer dimensions.
6. Select duct type (Circular or Rectangular) and silencer type (Straight or Bent).
7. Enter the silencer size.
8. Enter lengths X and Y (minimum 100 mm). Standard lengths are 650, 1250, 1850, 2450 mm, and +100 mm for cleanable units.
9. Press “Search”.

If no silencers meet the requirements, DIMsilencer may indicate this. Selecting “Yes” displays potential silencers. A common issue is an overly strict damping requirement. If no single silencer suffices, a combination may be needed.

Search results show values in various frequency bands; damping or self-generated emissions can be selected for display. Values not meeting requirements are highlighted in red.

Silencer performance

Enter Lw and select silencer

1. Press the “Silencer performance” button.
2. Indicate the silencer's placement (inlet air/outlet air, before/after fan).
3. Enter noise before the silencer, divided into frequency bands, with optional descriptive text. The interface displays damping, generation, Lw after silencer, and weighted sound pressure level.
4. Enter the intended air flow. Duct speed and pressure drop adjust with dimensions. Unreasonable values turn red and must be corrected.
5. Select duct type (Circular or Rectangular) on the right.
6. Select silencer type (Straight or Bent).
7. Available silencers appear in a scroll list; select the desired type.
8. Select size, noting the speed which varies with dimensions.
9. Select length.
10. Select baffle type for rectangular silencers.

The relevant silencer's performance data is displayed next to the requirements.

Tip: Use up/down arrows to find the best silencer by size or type.

11. When the correct silencer is found, press “Add to list”. The selected silencer and its technical data appear in the list. It can be named with a designation (e.g., LD11). More silencers can be added.
12. To search for or edit silencers, continue with steps 4-11.
13. Air flow, pressure drop, duct connection type, silencer type, and size are entered.
14. Press “Search silencer”.
15. Select from the list of results and add to the list.

The list of silencers can include multiple units that satisfy the requirement. Silencers can be removed for new searches. Once satisfied, save and print the calculation.

Calculation for premises

General explanations

DIMsilencer's “Calculation for premises” feature is a powerful tool for users who do not perform sound calculations in their CAD models. It calculates sound from the fan through to the premises, considering room damping, noise sources, and inlet/outlet air systems. Noise transfer between rooms is not included.

The process involves three stages in order: inserting premises, device, and fan. DIMsilencer automatically adjusts other selections based on these inputs.

Accurate knowledge of the installation is required to estimate flow in branches from the fan to the premises. The calculation structure allows for multiple similar premises to be calculated by saving and modifying components. Premises' properties and noise requirements can also be changed.

The upper window displays current sound pressure levels and requirements, while the central part shows calculated components for inlet/outlet air.

Specify premises data

1. Enter the premises name, length, width, and height.
2. Enter the premises' sound pressure requirement (Lp).
3. Select the room damping type from a list, which then presents the relevant alpha value and room damping R value.
4. Specify the number of inlet/outlet air devices and other noise sources (e.g., rotary coolers) in the premises.
5. Choose whether damping is calculated automatically or entered manually. Manual entry calculates the value directly, considering distance for direct fields.
6. Enter the location of devices and the distance 'r' to determine if the device is in the direct or reverberation field, referencing a graph.
7. Press “Add to list” when ready. Premises data appears in the top center windows for inlet and outlet air.

The top compilation shows current room noise level, noise requirement split between sources, and device count. If the distance to the first device is short, room damping has no effect; DIMsilencer calculates damping from the direct field and then considers other devices in the reverberation field.

Special: To set individual reverberation times, check the box to specify them per frequency band. The premises type setting is then deactivated, and premises reverberation times become visible for adjustment.

Insert device

Noise sources are inserted into the premises by pointing to the premises in the inlet air window and right-clicking or selecting “insert component”. The list then shows devices and noise sources. Select “insert device”. The lower section displays a structure with devices and a folder for custom devices.

Select devices and their current flow with pressure drop, then press “Add to list”. Repeat for the outlet air window. DIMsilencer detects outlet air and displays relevant devices.

Self-generated emissions can be read to estimate if a device meets room requirements or is too small. Devices contribute to total flow, with each carrying its own flow. DIMsilencer assumes equal Lw for both devices.

Insert another noise source

Highlight premises, choose “insert components”. If devices have been inserted, they are deactivated. Choose to insert another noise source. Enter the name and data, then press OK.

Insert fan

Highlight the inlet air device and choose “insert component”. Select “insert fan”. Created fans are displayed at the bottom left. To create a custom fan, select an existing one and modify it. Use “save” to save without inserting if multiple fans are being created.

To create and insert a fan, modify data and press “Add to list”. The fan is saved and added to the list, containing data for pressure and suction sides, usable for both inlet and outlet air.

Highlight the outlet air device, choose “insert component”, then “insert fan”. Enter suction side noise and press “Add to list”.

To create a separate folder, select “Lindab” in the left window, enter a new folder name, and create the article with data, saving or adding to the list. To alter fan data, select the fan, modify data, and press “Add to list”. Confirm replacement if prompted.

Insert distribution box

1. Highlight the inlet air device and choose “insert component”.
2. Enter box dimensions; the area is displayed.
3. Select the main connection location (ends or sides).
4. Select main connection type (circular or rectangular duct) and enter dimensions.
5. Specify if an internal baffle is present and if it has a double surface.
6. Select baffle installation method.
7. Enter width and height.
8. Select internal insulation type from the list.
9. If individual values are selected, enter them for each frequency.
10. Press “Add to list”.
11. To insert a box in outlet air, select the outlet air fan and repeat steps 1-10.

If ducts contact each other (end-to-end), it's considered an internally insulated duct, requiring a baffle. Product names can be changed by selecting the product in the calculation list and altering the designation. Data modification involves selecting the product, changing data, and pressing “Add to list”, confirming replacement if prompted.

Insert T-piece, X-pipe (Circular / Rectangular)

1. Highlight the product after which the T-piece is to be located, choose “insert component”.
2. Choose to insert T-piece.
3. Select circular or rectangular.
4. Select how noise is handled in the calculation.
5. Enter dimensions.
6. Enter flows for self-generated noise emissions.
7. Add to the list.

Repeat steps 1-7 for multiple T-pieces. If standing on a T-piece, the user is asked to replace it or add another. Product names can be altered in the product list. Components (except premises, devices, fans) can be removed.

Insert damper (Circular / Rectangular)

1. Highlight the product after which the damper is to be located, choose “insert component”.
2. Choose to insert damper.
3. Select from circular dampers or own dampers.
4. Enter flow and press. For own dampers, flow and pressure are read-only.
5. Add to the list.

Emissions for circular dampers are calculated by flow and pressure. Rectangular dampers require manual creation for specific flow/pressure and are selected under “own dampers”. Damper names can be changed in the project list.

Insert own component

Applies to all products: Highlight the product, choose “insert own component”, select from the list of own components, and add to the list.

Create component

1. Select the folder for the component.
2. Enter product name, flow, and pressure. Designation is entered after adding to the list. All entered data is static.
3. Use the save button to create multiple products simultaneously.

Lw before and Lw after are reported in the project list and during calculation review. Component names can be changed in the project list. Repeat steps 1-4 for several own components. The user will be asked to replace a selected component or add another.

Noise analysis

Analyse how much noise there is

The analysis occurs in the top left corner, showing noise levels in the premises and requirements for inlet/outlet air.

The right side indicates the number of specified noise sources. The calculation list shows Lw (noise output level) after each component.

This helps determine silencer placement. Analyze components generating noise to identify if fan noise or component noise is the primary factor. Often, it's a mixture, necessitating silencers in both locations.

Positioning a silencer and immediately reading the sound pressure in the premises is possible. Changes are displayed instantly when selecting different silencers. Suitable silencers are added to the list.

Search silencer

1. Indicate where the silencer should be placed in the calculation.
2. Choose to search for the silencer (right-click or use the search silencer button).
3. DIMsilencer enters the Lw before value. Descriptive text can be added. Select silencer type and dimensions. Speed in the connecting duct (high speed = high self-generated emissions) is shown.
4. Press “Search silencer”.

DIMsilencer attempts to find a silencer that meets premises noise requirements. If too much noise is present for a single silencer, a warning is issued.

5. Press “Yes”.
6. Move the selection box to view premises results and read sound pressure. Silencer selection updates the display. The total sound pressure figure changes from red to green when satisfied.
7. Add a suitable silencer to the list.
8. Continue placing silencers, following steps 1-7, until premises requirements are met. The red figure will turn black.

The distribution of sound requirements between inlet and outlet air can be adjusted by checking the distribution requirement box.

Save calculation

When the calculation for the first premises is ready, save it as “premises 1” (or a custom name). The calculation is named at the top of the screen.

For subsequent premises, save with a new name (e.g., “premises 2”). Remove irrelevant parts from the previous calculation and add new components. If premises are a new type, update their properties and requirements.

1. Select “Save as” under the File tab.
2. Name the calculation according to the premises.

Retrieve saved calculation

To continue from a previous calculation, select “Retrieve calculation” from the File tab.

Print

1. Press “Print”. DIMsilencer collects technical data for selected silencers.
2. In print preview, zoom in and out.
3. To change the printer, press the printer button, then “Select printer”, choose from available printers, and press OK.
4. Confirm the selected printer by pressing OK.

Tip: The printout can be saved as a PDF file.

DIMsilencer help

Calculating sound pressure

Results for room, inlet air, and outlet air are presented in tables, showing sound output from one or multiple noise sources, and total sound pressure.

Damping of sound from one device at distance r

Maximum damping (room damping R) is achieved in the reverberation field. Damping decreases closer to the device. A diagram illustrates damping based on distance 'r' and Q factor (location in the room).

Example: Device 1 damping = 1 dB, Device 2 = 4 dB, Device 3 = 4 dB. Resulting damping = 3 dB.

Damping in direct sound fields

Damping depends on the noise source location and alignment factor. Damping increases by 6 dB when the distance doubles. An example shows damping of a roof device at 1m distance is approximately 8 dB.

Damping in the reverberation field

Also known as room damping, it's independent of distance. Absorption area 'A' is obtained from room surfaces, absorption factor, reverberation time, and volume. Example: Damping with an absorption area of 10m² Sabine is 4 dB.

Formulas

Sound pressure in room

Lp = Lw(1) + 10*log(n) – D

Where:

• Lp: Sound pressure in room [dB]
• Lw(1): Sound output from one device [dB]
• n: Number of devices [-]
• D: Damping [dB]

NB: Assumes the same sound output from all noise sources.

DIMsilencer: Damping with one device at distance r, the remainder in the reverberation field

D = 10 * Log ( (q / (4 * π * r²)) + (n / A) )

Where:

• q: Alignment factor [-]
• r: Distance to device [m]
• A: Absorption area [m² Sabine]
• n: Number of devices [-]

Damping with one device at distance r

D(1) = 10 * Log ( q / (4 * π * r²) ) or D(1) = -10 Log10 (10^(-F(1)/10) + 10^(-R(1)/10))

Where:

• q: Alignment factor [-]
• r: Distance to device [m]
• A: Absorption area [m² Sabine]
• F: Free field damping [dB]
• R: Room damping [dB]

Damping in direct field (Free field damping)

F = 10 * Log ( q / (4 * π * r²) ) (Direct noise dominant)

Where:

• q: Alignment factor [-]
• r: Distance to device [m]

Damping in the reverberation field

D = R = 10 * Log ( 4 / A ) (Reflected noise dominant)

Where:

• A: Absorption area [m² Sabine]
• S: Restriction surface [m²]
• a: Absorption factor [-]
• V: Volume [m³]

T = 0.16 * (V / A) (Sabine's Formula)

Damping from all noise sources at relevant distances

D = 10 * Log ( 10^(-D(1)/10) + 10^(-D(2)/10) + ... + 10^(-D(n)/10) ) + 10*log(n)

Where:

• D(n): Damping device n [dB]
• n: Number of devices [-]