Thursday, 22 September 2016

Making it move

When pictures just aren't enough

Admitted, this one was mostly for the fun of it, but like most fun it taught me something useful.

I was at a conference recently, and was rather mesmerised by a some of the animations of modelled noise sources. But dBSea does not output animations, so I went the long way and got "Autohotkey", a program that lets you automate repetitive tasks, such as running dBSea's modelling algorithms 90 times over and moving the source in small increments between each image export. 
This process is essentially a batch process (i.e. running similar processes repeatedly), and can be very useful if you wish to run many models while systematically changing the input variables.

The below animation is what I came up with, a boat making it's way into Chesapeake Bay to "Bush Park Camping Resort". Note that the boat is travelling 180 km's in nine seconds (for your viewing pleasure), as the full eighteen hour video was a bit over the top for my laptop.
Boat sailing in through the mouth of Chesapeake Bay
It's important to outline that the results do not differ from using the "Moving source" option in dBSea, but for visual representation this is certainly more eyecatching.

Thank you for reading, please feel free to comment or ask questions below.

Resources:
https://autohotkey.com/
http://www.gebco.net/data_and_products/gridded_bathymetry_data/gebco_30_second_grid/

Friday, 9 September 2016

There's a real world out there

Integrating with GIS software

Often the modelling is just the beginning of a project, and inserting your modelling results in a real world context makes them immediately more relevant and easier to interpret.
From dBSea you can export into a range of formats, including .png and ESRI ascii (.asc) raster. The ascii format is very useful because it is geotagged, meaning GIS software will know where to put it, and that all features, such as the raster calculator tool or area calculation, is available to you.

Exporting visible levels to ESRI ascii raster to be used in QGIS

In the below illustration I used the GIS software to assess the extent to which the ferry from Mallorca to Ibiza masks the call of a humpback swimming by. (Masking is the process of making a signal indiscernible by adding noise)
dBSea is not strictly made for assessing masking, so I used the raster calculator in QGIS to find the area where the noise level from the ferry was 6 dB over that of a fictive calling humpback whale heading for Gibraltar. Because levels are exported in ascii format the GIS software is able to alter colours for the sound levels, and I can get creative with the presentation.

Two outputs from dBSea combined to indicate masking effect of underwater noise from ferry, exported from dSBea as ESRI ascii grid raster and imported straight into an "Eckert VI" projection of a world map.
The ability to export directly into GIS software mean that results can be easily and effectively put into context - especially if you're undertaking a large project where noise is just one of many concerns.


Please note that not much in this example is accurate as it is only meant as an example of possibilities.

Resources:

http://www.naturalearthdata.com/downloads/
https://www.qgis.org/en/site/forusers/download.html

Wednesday, 7 September 2016

dBSea 1.3.11

Tweaks for speed and adaptability

dBSea 1.3.11 is out and can be downloaded now.
the Basic version has also got an upgrade, and you don't need a license for that one.

So what has changed?

The nerdy stuff:
  • You can now adjust the dBSeaModes oversampling to suit the detail in your scenario.
  • The soundspeed profile interpolation is more robust regardless of input.
  • More efficient use of multicore when present.
  • Rendering of the results in the graphics window are now even faster.
The big difference:
The new thresholds from NOAA are now incorporated into dBSea, so you can evaluate those 24 hour SELcumulative levels properly. If you're using dBSea for impulsive sounds, we've included those thresholds too.  
Besides the five groups shown here, we also included sirenians (dugongs and manatees) in dBSea
And don't forget to have a look at the new example scenarios on the download page
(If you do not have a full version of dBSea, use dBSea Basic to view them)
Screenshots of some of the examples you can find on dbsea.co.uk/download


Tuesday, 23 August 2016

Less is More?

Is the more accurate model always better?

- Once more a "techy" post -

dBsea can be quite resource-intensive to run, especially if your model demands calculation of many sources and spatially detailed outputs.
Today I'll make a case for always running simple simulations until all parameters are set as wanted, or you are ready to run your model through the night. Even though dBSea is heavily optimised with respect to resource consumption, it is easy to make a model that demands huge amounts of calculations.
A comparison of calculation time versus accuracy of output seems to be the logical way forward.

Figure 1. A comparison of a coarse solve VS a detailed one, 5 minutes VS 3 hours. Top panes are the maximum levels projected to the surface, the middle shows exclusion zones and the bottom shows the 3D version with the calculation grid superimposed.
While the above solves are by no means identical, but sound levels are within circa 10 dB (see the spectrograms in the top panes), and exclusion zones are within a factor of 2. While this might seem like big differences, when you are designing you model, and want a bit off feedback on the changes you've made, a rapid update of the results is very desirable.

Another example is the below example (Figure 2), where two ray trace solves are very close to identical. Scenario "A" took over 30 min to compute, with thousands of outgoing rays from an approximated line source. Scenario "B" was very quick to solve with no calculation of attenuation, and only 20 outgoing rays. Also no frequencies over 1 kHz were included as attenuation means these frequencies do not propagate as far.
Figure 2. Comparison of a high accuracy solve VS a quick solve. dB-levels are only for comparison.
For quick evaluation and feedback during scenario design, simplifying your solves will radically improve this phase, making sure you only need to do the "big" solve once.

Thanks for reading, please don't hesitate to comment.




Friday, 1 July 2016

We get stuck

Today I had to resort to primitive methods for retrieving our Soundtrap logging device.

We had deployed it in Carlingford Lough in Ireland, not as much to measure anything specific as to get some insight into the soundscape of our local patch. The mouth of the Lough is quite busy, with big boats passing regularly, along with the occasional fisher boat and jet ski from the friendly local life guards (RNLI).


The hydrophone was attached to an anchor but with a separate line to the buoy to avoid unnecessary noise from the mooring. It's sitting close to the shipping channel, ready to record any passing ships. I should mention that we might get dolphins or porpoises as well, as this Soundtrap supports super high sampling rate, 576,000 samples per second!



The Soundtrap is deployed, safely hovering a couple of metres above the seabed. Yes, the sticker is upside down, I'll correct that later.

Long story short, our anchor was too good, and we had to send a diver down to retrieve both hydrophone and anchor. This meant waiting for slack water, which occurs when the tide is not moving water in or out of the Lough. Because of 4-5 metres difference in high and low tide, we could not send a diver down during the tidal race!

In the end we got our kit back.
It's always good to be reminded of the forces of nature - and strong anchors!




The sublime view from Cranfield Bay over the Irish Sea and the Cooley Peninsula. 

Thanks for reading!

Tuesday, 21 June 2016

If you'd just like a little taste

dBSea Basic - simple, but free

We've decided to do a free version of dBSea, so you can now use all the nifty visualisations and get to grip with how the software feels.The basic version only uses simple logarithmic spreading loss to estimate sound levels, but for illustration purposes this works nicely. Below i have three examples.
The first picture illustrates nicely the principle of spreading loss differences between a line- and a point-source. in the middle is a rough estimation of a tug-boat (included in dBSea-basic) sailing around the Isle of Man. The last illustration is one of pile-driving in the Moray Firth in scotland. 

Basic means basic. All of the calculations could be done in a spreadsheet or on your favourite calculator, dBSea-basic gives you that, along with our graphics rendering platform, and integrated species weighting functions.

I give a brief introduction in the video below:



Have fun, and spread the word.
Thanks for reading!

Thursday, 16 June 2016

New update of dBSea - while we wait for 2.0

A smarter, more streamlined dBSea

dSBea 1.3.10 has hit our webpage. While not much has happened on the graphical output side, quite a bit of work has been done on the inner workings of the solvers, along with some productivity tweaks.

So if you've never seen dBSea before, this post might not be for you, but by all means, feel free to read on anyway! (and download a copy)

The Parabolic equation solver has got an overhaul, and now uses "Greene's Approximation" for first steps, unless the user decides to use any number of Padé terms. These two methods allow the Parabolic Equation solver to have a much broader sound emission angle from the source.
While this sounds very technical, it means that sound will now propagate in a more realistic fashion from the source - this is especially important for accurately predicting more complex scenarios. We have also improved on the energy coupling algorithm to facilitate even steeper propagation angles.



To make the solving even faster solvers now stop when they reach land (unless you choose otherwise)

We have included a slider for you to select the number of CPU-cores you want to use, so you can keep some of your processors for other tasks.

dBSeaModes modal solver is now even faster!

We have changed the way the total time of the scenario is set, so it is now harder to misunderstand exposure levels due to differences in exposure time.

For quick checks of your solution, we've added 20log and 10log transmission loss lines to the cross-section plot. This plot allows a radial view of all the calculated transmission losses and is a very useful tool for investigating results.


Thanks for reading!

We are working hard on a dBSea 2.0, and rumour has it that it will feature full 3D-solvers!


(By the way, this post was all done with examples from dBSea running in linux (wine usp10.dll set to native, then built-in))