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Digital voice recorder
Sound recording has many uses in e-learning; commentaries for stills and videos, interviews showing different points of view to spark discussion – used in a classroom or from a Web page or vle – and simple podcasts for exposition.
Sound recording has many uses in e-learning; commentaries for stills and videos, interviews showing different points of view to spark discussion – used in a classroom or from a Web page or vle – and simple podcasts for exposition. Most modern computers can record high quality sound, but I find that a small dictation voice recorder can provide extra flexibility and allow recording on the fly without dragging a laptop around.
Page contents
Overview
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The Olympus WS-200s sound recorder is available cheaply in the UK and the ‘high quality mono’ setting can provide more than adequate audio capture for speech and for interviews – certainly better than the ‘shoe box’ cassette recorders we used years ago. Olympus seem to be the main manufacturer of digital speech recorders, Sony have a few models. Some MP3 players can record and have microphone sockets, but I find the WS-200s to be ergonomic and to have relatively idiot-proof menus and settings. I especially like the way the battery compartment slides off to reveal the usb connector – no cables to break and no hinges to damage. Others have had problems with the battery compartment cover springing open, but, so far, I have not had this issue.
Using an external dynamic microphone considerably improves the quality of the recordings; the photo above shows a microphone and a ‘mini-disc lead’. These leads connect the mono unbalanced output of the dynamic microphone to a stereo mini-jack connector via a short lead. No messy stacked adaptors and less stress on the microphone socket of the recorder.
This is a consumer product and models and configurations change quite quickly. Olympus seem to have standardised the format however and there will probably be something in the £80 to £100 price range available for some time.
Hints and tips
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- Your computer is the best sound recorder you have but isn’t really portable and has short battery life
- The Olympus Digital Voice Recorders are very small and the AAA battery lasts many hours (but always have a spare)
- They record AM radio quality sound [32kb/s] in WMA format. You can record 8 hours in ‘hq’ mono mode.
- Use an external microphone, the internals are OK for dictation or for recording meetings but don’t give a ‘full range’ of tone
- Dynamic microphones work well, I have tried 600 Ohm and 200 Ohm mics with relatively high outputs.
- Peak level of -6 dB and a noise floor of roughly -48 dB are typical results
- A mono XLR to 3.5mm Stereo minijack cable is a useful addition as it shortens the cable and reduces the stress on the WS-200S microphone socket.
- Loop the cable once and hold the loop against the mic with the same hand you are holding the mic with. This will reduce a lot of the handling noise
- Line matching transformers make the signal to noise ratio worse. The WS-200 has an input impedance of 2000 Ω (2KΩ) and most matching transformers match up to 50 KΩ
- I convert sound files from WMA compressed formats to WAV uncrompressed format, and then edit that in Audacity (which cannot import WMA files directly).
- I export as MP3 files at a bit rate of 32 or 48 Kb/s.
- If no editing is needed, most modern computers can play WMA files directly
Resources
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- Nice page with photos and some samples of sound with a good reporter’s microphone
- Olympus specifications page that gives the sampling rates
- David Battino’s comparison of three Olympus sound recorders
- Review by Andy Carvin with pictures and a sample blog
- Microphone advice from the BBC – I think the waterproofing strategy is a joke
- Easy WMA format converter for Mac OS Panther upwards $10 shareware but does what it says on the packet
- Windows WMA to WAV, MP3 converter free but nag screen for a few seconds when starting.
- NCH do a free converter and a free transcription application for Windows and Mac OS 10. The Express Scribe software helps when ‘logging’ tapes.
- Audacity open source sound recorder same interface on the Mac, Windows and Linux. Follow the instructions if MP3 export is needed
Samples of sound
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These sample recordings have been converted to Wav, trimmed in Audacity without level change, and then converted to MP3. That is how I will be using most of the sound that I produce with the recorder.
- Raw WMA file from WS-200s: internal microphone [300 Kb wma]
- Raw WMA file from WS-200s: external microphone [300 Kb wma]
- Added Sept 06: Context of the recordings above
- Recording from the WS-200s using the internal microphones [810 Kb mp3 ]
- Recording from the WS-200S using a cheap dynamic microphone with the gain setting set to low [ 900 Kb MP3 ]
- Suburban train pulling out of a station using an external hand held mike with windshield. Mono HQ mode and gain setting on ‘HI’. I used the Audacity high pass filter with a cut off frequency of 220Hz to reduce the rumble from the train on this recording.
Original blog posts
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I’ll refactor this over time
May 2006: I’ve just taken delivery of an Olympus WS-200S Digital Voice Recorder to replace my ancient cassette (yes, tape) recorder that now can’t quite generate enough torque to play a cassette..
As you can see from the snap above, the Olympus recorder itself is tiny and is dwarfed by the external microphone jack, let alone the microphone itself! The external microphone, even the cheap dynamic microphone shown above (Dixons in the UK used to sell these for about a tenner), provides a considerable quality boost over the internal microphones. The signal level from the dynamic microphone is suprisingly high to the extent that I can use the lower gain setting and reduce the hiss somewhat. The input impedance of the WS-200S preamp is given as 2Kohm so I suppose the mismatch from the 600 ohm impedance of the microphone isn’t that great.
Listen to these two samples (just under 2 minutes each)...
The overall quality with the external microphone is warmer but with a little more hiss when compared to the Logitech USB microphone fed direct into my iBook. The Olympus unit is a lot more portable however, and the AAA battery will provide 12 hours of recording. The high quality mono mode samples at 44.1 KHz and records at a bit rate of 32 Kb/s. Previous Olympus models recorded at 64Kb/s apparently so the compression is higher on these new machines.
When you have completed your recordings, you can slide the silver plastic battery unit off to reveal a usb plug – the entire recorder can just plug right into a USB socket, no need for a cable.
The Olympus voice recorders all save in Windows Media Audio (.WMA) format, which the Windows Media Player can handle – there is no software with the device. Apparently there are WMA editors available, I’ll be checking the Windows software situation over the next few weeks.
On the Mac QuickTime can play the files using the Windows Media Player plug in but you need to convert the WMA files to another format for editing. EasyWMA is a shareware ($10) application that can do the file conversion. I prefer to convert the WMA files to WAV files using easywma as WAV is an uncompressed format. I then edit the WMA files in Audacity and convert to MP3, the ‘standard’ file type for podcasts, at a 64kb/s sample rate. I’m still experimenting with this – when I tried exporting MP3s at a 32Kb/s rate there were ‘metallic’ aliasing effects in the output. The BBC use a 56Kb/s rate for their podcasts of radio talks.
Some reviews and information about the WS-200S is available, and these reviews were a factor in my decision to drop the plastic.
- Nice page with photos and some samples of sound with a good reporter’s microphone
- Olympus specifications page that gives the sampling rates
- David Battino’s comparison of three Olympus sound recorders
- Review by Andy Carvin with pictures and a sample blog
Stand by for some location based podcasts soon…
Note added 2nd June: tried a line matching transformer (500 ohm to 50Kohm) and the sound levels dropped. This might be expected from the 2000 Ohm quoted input impedance of the pre-amplifier within the WS-200S – a 50Kohm source impedance is very high compared to 2000 Ohms and will result in attenuation of the signal. This tends to go against the advice of Mindy McAdams who is using a line matching transformer with her Electro Voice reporter’s dynamic microphone. I contradict Mindy with some trepidation as she is the author of the wonderful Flash Journalism book.
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bodmas.org, 4 June 2006