What is Strutt?

Strutt is Arup's Acoustic Calculation Software. It is designed to help acoustic engineers to undertake acoustic calculations by using standardised equations and functions (for example, inserting fan noise levels, transmission losses of elements, logarithmic addition and barrier loss calculations).

Specifically, it is a Microsoft Excel Add-In that provides access via the Strutt menu to a whole host of standard acoustic calculation elements. So Strutt runs under Excel allowing you to use all the power and familiarity of Excel to do your calculations.

What isn't Strutt?

Strutt is not a piece of standalone software - it runs under Microsoft Excel, so you can still do whatever you want with the calculations in Excel.

Nor is it a set of standardised calculations. It will not force you to do anything you don't want to do (except change the number or location of columns in the spreadsheet). It is only 'helper' software; providing help to undertake your calculations more quickly, and accurately by using QA checked and approved functions.

How do I use Strutt?

You simply select the row in the spreadsheet where you want to put in a calculation (anywhere in the row, it doesn't matter), and then select the calculation element you wish to include from the Strutt (or right-click) menu. The calculation parameters can then be selected from other rows. Functions that have input parameters that you might want to vary have these pasted onto the worksheet as input cells, so that you can easily change the parameters. Strutt then pastes an appropriate function into the cells. It's pretty simple! As with Excel, whenever you update a cell, all the calculations will automatically be updated.

If you want to create a new calculation sheet or add rows, or delete rows, you can also select these features from the Strutt menu.

What will Strutt help me do?

It will help you do acoustics calculations faster, and more accurately. It does this by helping you to input standard input data (eg. fan noise levels, sound levels, transmission losses), applying standard acoustic equations (eg. Logarithmic addition, Barrier loss, reverberant noise levels), and calculating outcomes (eg A-weighting, NR ratings).

It will also help you manipulate Excel to add new formatted calculation worksheets, and insert and delete calculation rows.

What won't Strutt do?

It won't do the 'whole calculation' for you. You've still got to think about what you're trying to achieve, and use the right calculation elements to properly undertake your calculation. But it won't stop you from using any of the standard Excel mathematical, statistical or graphing functions within your spreadsheet, like you would normally do.

Strutt also doesn't lock any of the input or results cells on any worksheet. This is a tad dangerous, since you, the user, could type over stuff and break things; but you can do that anyway now, and we didn't want to take away any of your ability to do what you want. You have the power, just act responsibly.

Oh, and it won't Undo more than once. Sorry. See: One level of Undo?

Where did you get the formulas from?

The functions implemented in Strutt are sourced from a variety of locations, including the Arup Mechanical Services Guide, reference texts such as the Woods Guide, Bies & Hanson, Laymon Miller, and particular Standards (eg ISO140).

How do I know that they are right?

Strutt has been extensively QA checked. There is even a QA check spreadsheet which has separate sheets to verify every implemented function against the original equations.

Can I use the functions independent of the Strutt ribbon interface?

Of course. You can use them manually by typing the function name directly into a cell using the required syntax. For functions like =dbAdd() this can be very handy. However, generally the syntax is quite complicated (and we haven't yet published a function syntax reference) so it is probably generally easier to use the Strutt Ribbon to help you insert the functions automatically into your spreadsheet. Because the functionality of Excel is maintained, you can inspect and change any cells you want.

Does it work in Metric and Imperial Units?

Yup. Simply select Metric or Imperial units from Strutt|Settings|Preferences, and everything from then on will be input in your selected units. Note that it does not change the units of any pre-existing data.

(For those who must know, all equations are implemented within Strutt in Metric Units, and the Imperial preference simply includes a conversion factor on each input parameter).

Do I have to use one of the standard 'Calculation Worksheets'?

Strictly no, but you'd be mad not to. Strutt works quite simply by pasting functions into the current worksheet. However it makes the assumption that the spreadsheet is arranged with the particular column structure in the templates. The standard 'Calculation Worksheets' are arranged in the right way, so Strutt drops stuff into the correct columns.

Why does it get things wrong if I insert or delete columns?

As noted in Do I have to use the standard 'Calculation Worksheet'?, Strutt works on the basis that it simply pastes information into particular columns. If you go and change the location of the columns (eg by inserting or deleting columns in Excel, which you can do, since nothing is locked), then it'll muck up the correct ordering of the columns, and stuff won't end up pasted in the right place.

What's the deal with input cells in the Rating, dB and dB(A) results columns?

The standard calc sheet has Ratings, dB and dB(A) results columns to the left of the octave band columns. However, sometimes it's convenient to use these for parameter input values (such as duct lengths etc.) that the user might want to change. So really, these are 'multi-purpose' columns that hold both 'inputs' used in the calculation and 'results' from row-operators such as dB, dB(A) and NR calculations.

Does it use a + ve or - ve sign convention?

Strutt uses a totally + ve sign convention. ie all losses are to be shown as negative values. It is therefore only necessary to ever add rows together to get a result. This reduces the potential for confusion between users (since it is immediately apparent which rows are subtracted (they're the ones with the negative values) and which are added to the result.

Some inbuilt formulas (such as Composite TL), are actually smart enough to check what you've done, and give the correct result regardless of whether you use + ve or - ve input values (you should, of course, use - ve values for Transmission Losses).

How come there is no 'user & job no.' information input function?

Actually there is. We didn't really want one, but succumbed to the pressure. Strutt will automatically put the 'Initials' from Strutt|Settings|Preferences into the 'by' cell on the standard calculation sheets. Additionally, you can enter the Job Title, Job Number and Suffix into Strutt|Preferences|Job Details and they will be automatically inserted onto every new sheet in the workbook. Updating the relevant job number and title cells in any sheet will also update these details for the particular workbook.

One level of Undo?

We know this is a really annoying, but believe it or not, Microsoft make implementing Undo in Excel ridiculously difficult. It basically requires versions of the spreadsheet to be saved after every user action. Multiple levels of Undo is even more of a pain, since multiple versions of the spreadsheet must be saved, one after the other. This greatly increases the complexity of the software beyond what we were reasonably able to achieve at this stage - we have concentrated on getting the acoustics bits worked out.

So there's only one level of Undo. That's generally enough to get you out of most trouble.

I found a problem, or have an idea for an additional function, who do I contact?

Hmmm. Probably best to send an email to Strutt@arup.com. We'll see what we can do.

How long will it take to issue bug fixes or add additional functions?

Unfortunately, that depends. If it's a simple problem, we hope to be able to fix it straight-away. If it's a feature request, then it will depend on:

  • How difficult it is to implement (some apparently simple features actually require massive amounts of programming)
  • How necessary it is
  • How much time we've got at any particular stage

In any case, we issue regular updates (at least every six months) as we add new functions and feature requests. We want to improve Strutt even more!

Where did you get the idea?

Arup Acoustics developed the first versions of Strutt in 2006 for use internally. At that time (and today) there's nothing decent commercially available, and it was difficult to conceive exactly the right way to go about it which ensures technically robust calculations, but still allows room for flexibility and creativity in the process.

Strutt is similar in concept to some old-but-effective DOS software called Acoustic Calculation Software (ACS) that was developed at Sandy Brown in the UK, and a bit like Sound Science's NoiseWorks - but much more comprehensive and much easier to use.

Since 2006, Strutt has been subject to the daily rigours of use by our engineers throughout the world - and constantly updated and improved into the robust and comprehensive software that you see today.

Why are you selling it commercially, not just keeping all the Strutty goodness for yourselves?

Making Strutt available to other acoustic engineers outside of Arup took a lot of negotiation. But we believe that allowing other acoustic engineers and consultants to use Strutt helps Arup with its wider mission to help ‘Shape a better world’, and advance the acoustic profession more generally. We also hope that releasing it more widely than ‘just us’, will expose us to a wider range of ideas for improvement, which helps create better software and helps us raise our game too. Finally, the commercial income from selling Strutt allows us to defray some (but certainly not all) of the (not insignificant) development cost. Trust us – we’re not in this for the money (clearly, it’s the fame and prestige!).

Who developed it?

Strutt has been developed by the following people; Ian Knowles in London wrote the brief and kick-started the development. The concept and software was originally implemented by Kym Burgemeister and Cameron Hough. Strutt has been greatly improved and extensively re-written for commercial release by Kai Fisher and Kim Jones.

We have all been assisted by input and/or comments from, in no particular order (and with apologies in advance to anyone missed), Ian Knowles, Rob Harris, Jon Osborne, Paul Adams, Nick Antonio, Paul Malpas, Nick Boulter, Raj Patel, Kurt Graffy, Chris Field, Sylvia Jones, Vahndi Minah, Larry Tedford and Frank Butera.

Why is the software called Strutt?

Strutt is named after John William Strutt OM, PRS, who was the 3rd Baron Rayleigh, and commonly known as Lord Rayleigh. Rayleigh was an english physicist who is the 'father' of modern acoustics practice who published his seminal textbook The Theory of Sound in 1894, and won the Nobel Prize for Physics in 1904.

In addition, Struts (with only one 't') are also 'structural elements used to strengthen a framework' which references not only the calculation paradigm adopted when using Strutt, but also the Structural Engineering heritage of Arup.

To get a free trial copy of Strutt, or to find out more about how Strutt can help you, please contact us at: