Sometimes work and pleasure come together. In my case, both involve sound.

Last week I logged on to the European Society of Radiology website to check some ultrasound medical conference info, and was thrilled to be greeted by an intro splashscreen featuring birdsong.

Sadly, I immediately recognised a Song Sparrow in the habitat recording. Here was a proud professional European organisation advertising itself with a generic North American soundtrack (well, how would they know?!)

Naturally, I e-mailed the site to complain, and offered one of my own recordings from the UK, which I am pleased to say they were thrilled to accept.

So now if you go to www.myESR.org you can hear a Northumbrian dawn chorus in its rightful place (I also put in a Roe deer bark as a signature call; our annual conference is in Vienna, and Austrians do like a bit of “Reh” for dinner…)

Osprey

At this time of year, late October, you’ll find deep piles of stinking, rotting seaweed at high tide level in many places along the coast of Northumberland. I hope that’s put you off visiting. Job done – too many tourists already.

But I love the stuff. It’s alive! Not only full of invertebrates, but stick your mics into it and it makes a lovely, crackly, bubbly sound that none of your friends will be able to identify. Of course, after coming out of a day’s session recording in there, you might not have any ‘close’ friends left.

So I’ve just returned from a great day splodging around, to the amusement of several labradors and their owners, placing a couple of Sennheisers in the chosen location, and cabling 100m back to my car on the cliff top. The idea was to get the close up calls of feeding birds – mostly redshank, plus turnstone, pipits, wagtails, starlings and the odd crow.

Redshank_turnstone

The trick is to observe where they like best, then keep turning over the seaweed in front of the mics every hour or so, to reveal a fresh layer of creepy-crawlies. This is a very effective technique, especially as in this particular location the birds are used to regular human disturbance, and will edge back to the ‘bird table’ within a few minutes. I recommend a low tide and an offshore wind to flatten the waves (sadly today the sea was a bit too big).

Most people just walk past rotting seaweed, holding their breath, but for the wildlife sound recordist, invertebrates = food = birds = a recording opportunity.

Carpe diem.

Osprey

A cautionary tale
I am having such fun with my ultrasonic microphone that I made a special journey to a known Barbastelle site. This is a rare species with only a few known maternity roosts in the entire country.

I arrived in good time before sunset to get my bearings. The site turned out to be a National Trust owned woodland with a network of public footpaths plus a convenient lay-by for parking; absolutely ideal!

Firstly, I selected a mature Oak tree in a hedgerow where I deployed my heterodyne detector, tuned to 36kHz, feeding the signal to an unattended recorder.

Then for my full-spectrum kit, I found a glade within the main wood with a gap in the canopy and some understory, which I correctly assumed would be good for biodiversity.

I was blasé about the machines working in the harvest fields nearby and amplified music from some distant village. I never worry about such distractions when targeting bats as the frequency difference is enough to separate the valid signal from ambient noise.

However, this is a cautionary tale for unbeknown to me, a male bush-cricket (Pholidoptera griseoaptera) was sitting close to the microphone. I cannot hear them nowadays and as I explained, I had just parked my bionic ear.

Then I retreated and sat bravely in my folding chair for an hour, serenaded by Tawny Owls and a Muntjac, as the light faded.

File size limitations
I mention the time duration because on my system, the maximum WAV file size is 2GB which equates to 62 minutes at 192/24 on one channel.

This is more than enough for my purposes and a quantum improvement over the niggardly < 2 seconds available on the early time-expansion machines.

Later at home when I had transferred the files to my PC, I was pleased to find that the Barbastelles had performed on cue and I had numerous well-modulated ecolocation sequences.

Unfortunately, my bush-cricket had also made known his presence, stridulating without a single pause masking Barbastelle pulses, on the sonograms. Mmm!  Of course officially, I am in favour of biodiversity!   Doubtless, the bat recordings are repeatable and next time I will be more circumspect!

I cannot do justice to sonograms here but instead, I include a Tawny Owl protesting at my presence. Full-spectrum recording captures normal audio as well, so here is a ‘by product’ of the session. Tawny_Owl

The main problem with ultrasonic recording  is the need to review all the material back home on a PC when it is a forensic and painstaking  job checking through the file visually. But then, how better to spend an evening ?

Finally, I would encourage mainstream wildlife recordists to cast their net more widely and target the ultrasonic world. It is a rewarding genre and new discoveries await.

But one final word of warning… Remember, nothing propinks like propinquity!

Prolix

 Spring is the breeding season for birds but our native bats are just starting their courtship behaviour. Furthermore, as the days get shorter, bats become active earlier, at a more convenient hour.

Listen here to a territorial male Noctule recorded via my heterodyne detector. Noctule

Full-spectrum recording

Now, conventional detectors have their uses but they also have limitations and I now favour unadulterated full-spectrum recordings rather than using derived signals.

You need a 192 kHz sampling rate and a spectrogram facility so practising recordists using a modern CF-card recorder and PC editing software have the basic equipment to get started. Then you need a microphone with an extended frequency response such as the trendy WM61 capsule, which is a lot cheaper than a bat detector.

I am enthusiastic about the capabilities of my kit that has taken my understanding of the Chiroptera to a new level. It really is a quantum advance for survey work and that is not hyperbole!

I am having to teach myself heuristically but I am making headway. I am finding new local records all the time and it turns out that some so-called rarities are more elusive than really rare.

For example, I have been trying to locate Serotine feeding sites for years and in August, I finally tracked them down making several recordings that translated into presentable sonograms, although they do not reproduce well here.

Serotine ecolocation pulses

Wing clapping during courtship has been reported, so there is a target for an ambitious sound recordist!

Dynamic range
Dynamic range is an issue for the sound pressures can be very high at short range and I frequently over-record the ‘loud’ species.

In contrast, when recording at high gain, I often capture the elusive Brown Long-eared Bat (Plecotus auritus). This is common enough and is variously known as the ‘gleaning’ or ‘whispering’ bat. The literature states that its radar is too ‘quiet’ to register but over the summer, I have logged quite a few contacts.

I would encourage mainstream wildlife recordists to cast their net more widely and target the ultrasonic world.  It is a rewarding genre and new discoveries await.

Prolix