Review: Dodotronic Ultramic 200K/250K

The Dodotronic Ultramic is an ultrasonic microphone with a USB plug. It offers full spectrum real time digital ultrasonic recording for less than 300 Euros (plus a laptop). I have been using these microphones in the UK and the Philippines for the last 18 months, and I consider it the most exciting (and affordable) development in the world of bat detectors for many years. Here’s why.


1.    It allows real time full spectrum sound to be both recorded and visualised in real time. Real time full spectrum recording provides an unambiguous permanent record of bat sound that is superior to data collected by any other method.  
2.    It is lightweight – can be easily fixed to almost anything with electrical tape, including tree branches, washing lines and car radio antennae.
3.    It is tough –  Dodotronic microphones are housed in an sturdy aluminium tube and have no external moving parts. My microphones have been trodden on,  dropped and suffered impacts that would destroy most bat detectors.
4.    Easy to use – just plug the microphone into a laptop, open Audacity, select the microphone and the appropriate sample rate and press record. Using seawave to record and view spectrograms in real time is almost as simple.
5.    Works on Windows or Mac systems plus Linux Ubunti and Debian (although only the 100Khz version works with Windows XP)
6.    Capable of making quality recordings of bird song, amphibian calls, human speech
7.    From about £265 including delivery and VAT the microphones are much cheaper than any other method of recording full spectrum bat sound in real time (assuming you already have a laptop).
8.    Three gain levels set with two easily accessible switches inside the device.
I’ve used the microphones in the following contexts:
Surveys for planning applications: The first time I used a Dodotronic microphone was at a site with a lot of bats that I had surveyed with a highly experienced colleague the week before with heterodyne and time expansion detectors. Within three minutes of turning the microphone on we found a species we had presumably missed before, and the following morning  identified another species on the basis of distinctive social calls we had recorded.  Since then I’ve used them as the core component of all commercial survey work because they provide a full record of audible bat activity at the site together with a unique record of background noises at the site that can make the origins of the recording undisputable. Each recording system usually consists of a Dodotronic 200K microphone and a Panasonic Toughbook CF-28 with 512MB of memory running Windows XP or a 250K microphone with an Asus netbook.
Local Bat Group use: Because the microphone is relatively cheap, difficult to break and easy to use I loan one to members of the local bat group, who connect it to their laptops and make recordings of bats in different parts of town. All the recordings are time stamped so these amateur surveys aren’t vulnerable to poor note taking, and species ID can be verified by more experienced members if necessary.  The devices allowed us to accumulate a large amount of data about the distribution of bats in the town over a single summer.
Highly diverse tropical bat communities. The Philippines has some of the most species rich bat communities on Earth and a committed group of highly competent and experienced field workers, but bat surveys almost invariably rely on capturing animals and the use of ultrasound detectors has been very limited. Heterodyne and frequency division systems are unsuitable for highly speciose habitats and time expansion devices are prohibitively expensive. Colleagues in northern central and southern areas of the Philippines now have Dodotronic microphones which they use to record high quality ultrasound around the country. I have tested the microphones in a variety of habitats including city centres and dipterocarp rainforests.    
Survey techniques. I have used Dodotronic microphones for static surveys and for transects by car, bicycle and on foot.   I fix them to landmarks, wing mirrors, handbars and car antennae with electrical tape I waterproof them when necessary in plastic boxes, tents, or by wrapping them in cling film. For the ultimate geek look you can tape it to your hat. In practical terms the uses of the device are mainly constrained by the device it is connected to. Laptop battery power tends to be a major factor and many old models function perfectly but have weak batteries. Often it is economical to buy one or more generic batteries to allow dusk to dawn surveying.  Transects on foot or by bicycle require a light tablet or notebook rather than a bulky laptop. I expected that jolting from bicycle rides would prevent data being written to the hard drive correctly but this has not been an issue so far.

Dodotronic microphone in use on Shire Hill, Glossop
The simplicity of the Dodotronic microphones means they can easily be used by anybody who has basic computer skills.  They are tough, sensitive, reliable and inexpensive, so why haven’t they revolutionised bat detecting already? One  reason is that they do not work with smart phones, because smart phones cannot sample sound at the 200/250 KhZ rates required. There are rumours that this problem will be solved by cunning technology in the near future. Otherwise I cannot think of any reason why this extraordinary device should not be massively popular.
Dodotronic microphones record up to 100 or 120KhZ depending on the model and do not require drivers. The 100KHZ version is compatible with Windows XP, 7 and Vista, as well as Mac OS and Linux Ubuntu and Devian, the 120KHZ version is not compatible with Windows XP.  

Update 25th March 2012 - Ultramics now work with Android Tablets

Update 5 May 2015 - Ultramics do not work with Windows 8 because they accept a sample rate of 384 Khz. Thanks to Martin Love for the information.

Daniel Bennett, Mampam Conservation.