Voice activation changes everything
A recorder running continuously fills its memory and flattens its battery in hours. One that starts on sound and stops on silence can sit for weeks and capture only what matters, which is why voice activation is the single most useful feature on this page. If you are leaving a recorder somewhere rather than carrying it, treat it as essential rather than optional.
After that it is a question of form. Pocket recorders are simplest. Pen and USB models look like ordinary objects on a desk. Watch and keyring models stay on you. Recording capacity and battery life scale roughly with size, so the smallest models trade runtime for discretion.
Live listening
Some units go further and transmit rather than store, letting you listen live from anywhere over the mobile network. Those are on the listening devices page, along with 4G trackers that combine location and audio.
Voice activation, and what it costs you
Voice activation means the recorder sits idle until it hears sound above a threshold, then records until the room goes quiet again. It is the difference between a device that runs for a day and one that runs for weeks, and it is the single feature that decides whether a recorder is useful for long unattended jobs.
The trade is the start of each sentence. Every unit takes a moment to wake, so the first word or two can be clipped. Better units buffer continuously and keep the second before the trigger, which removes the problem. If the recording has to be complete rather than indicative, check whether the unit does that or set it to record continuously and accept the shorter runtime.
Battery and capacity, in hours rather than numbers
Capacity is rarely the limit. Audio is small: 8GB holds hundreds of hours at ordinary quality, so a recorder almost always runs out of battery long before it runs out of card.
Battery figures are quoted at the most favourable setting, usually the lowest bitrate with voice activation on. A unit advertised at several weeks may run a few days recording continuously at high quality. Decide which of those two you are doing, then read the figure that matches.
Where you put it matters more than the microphone
Recorders fail on placement far more often than on specification. Sound reflects off hard surfaces and gets absorbed by soft ones, so a unit inside a bag or a pocket records fabric. On a table between speakers it records the conversation. Near a fridge, an air conditioner or a road, it records the fridge, the air conditioner or the road, because the microphone has no way to prefer a voice.
If a recording matters, do a five minute test in the same place first and listen back on headphones. It is the cheapest thing you can do and it catches these problems while they still cost you nothing.
Getting the audio off
Most units here appear as a USB drive when plugged into a computer, so files copy across with no software to install and nothing to sign into. Check the file format if you plan to work with the audio: WAV is uncompressed and large, MP3 is compressed and small, and some units record in a proprietary format that needs a converter.
Common questions
How long will it record? Continuously, several hours to a couple of days depending on size. On voice activation, weeks.
Is it legal to record a conversation? Audio carries different rules from video in New Zealand. Check what applies before recording a conversation.