THE NATURE LOVER'S BLOG

SONG METER COMPARISON

07 april 2025

 

With the arrival of spring, it is also the ideal time to begin bat monitoring using ultrasonic recordings. Whether you are a researcher or just starting out in the world of bioacoustics, having the equipment that best suits your needs is essential for obtaining high-quality recordings and reliable data.

Wildlife Acoustics offers two ultrasonic recorders in its catalog: the SM4BAT FS and the SM MINI BAT 2, the latter available in two models: one powered by AA batteries and another with lithium batteries.

But which one is the most suitable for each case? Below, we analyze the key differences between these two devices to help you make your choice.

 

 

 

SM4 BAT FS

SM MINI BAT 2
   PRICE

1.545,00 €

with SMM-U2 microphone icluded               

 AA:      875,00 €
Li-ion:  995,00 €

   AUTONOMÍA DE LA BATERÍA

 Up to 48 ten-hour nights             AA:      Up to 50 ten-hour nights
Li.ion:  Up to 125 ten-hour nights

   CONNECTOR DE ALIMENTACIÓN EXTERNA       

Yes No

   EXTERNAL POWER CONNECTOR

Yes No
   USER INTERFACE Buttons / screen iOS or Android app via Bluetooth
Computer configurator Computer configurator

   GRABACIÓN DE AVES / RANAS

 No Yes, with additional acoustic microphone        
   TRIGGERING TECHNOLOGY Narrow-band (more sensitive in noisy environments) Broadband

  WARRANTY

 3 years detector 2 years detector
   MEMORY STORAGE

2 SD cards (up to 2 TB each)

1 SD card (up to 2 TB)

  RECORDING FORMAT

16-bit full-spectrum (WAV)

16-bit full-spectrum (WAV) and
Zero-Crossing (ZC)
  BATTERY TYPE

4 D sized alkaline or NiMH

 AA:      4 or 8 AA alkaline or NiMH
Li-ion:  1-6 Li-ion 18650

 

Discover the ultrasound recorders

 

Do you have questions about the new generation of Wildlife Acoustics recorders?

We know that choosing the right recorder can be tricky, especially with the second generation of equipment that was released last year. That's why we've compiled the most frequently asked questions about the SM4BAT FS, the SM MINI BAT 2, and other Wildlife Acoustics models to help you resolve any issues.

From technical differences to tips for optimizing your setup, here you'll find all the essential information to get the most out of your device.

 

What is the lowest frequency the Song Meter Mini Bat's ultrasonic microphone can record?

The ultrasonic microphone built into the Song Meter Mini Bat (generations 1 and 2) has a permanent high-pass filter (HPF) with a cutoff frequency of 8.25 kHz. An HPF is a filter designed to remove incoming signals below its cutoff frequency. In the case of the Song Meter Mini Bat, the purpose of the HPF is to prevent low-frequency sounds like wind from distorting your recordings or excessively triggering the recorder.

Most filters take effect gradually as frequency changes. In the case of the Song Meter Mini Bat, for each factor of 2 below the cutoff frequency, sound at that frequency is reduced in volume by 12 dB compared to sound above the cutoff frequency. For example, sound at 4.13 kHz is reduced by 12 dB, and sound at 2.06 kHz is reduced by 24 dB.

You should only expect to record sound as low as approximately 8 kHz, but you may still see slightly lower-frequency sounds recorded if they are particularly loud.

If want to consistently record lower-frequency sound, you should install an acoustic stub microphone on your Song Meter Mini Bat and schedule the recorder for acoustic recording.

 

Are there acoustic differences between the first- and second-generation Mini Bat recorders?

While the acoustic properties of both models are largely the same below 70kHz, the new Mini Bat 2 is more sensitive to sounds above 70kHz. This means that echolocations above that frequency (e.g. UK Horseshoe bats) will be clearer in the recordings, and more distant echolocations can be picked up.

 

Why new models? What is different about them?

Wildlife Acoustics proactively seeks out, listens to, and values our customers’ feedback. The new Song Meter Mini 2 and Mini Bat 2 address feedback shared by customers after spending millions of collective hours in the field recording with our first-generation models. Improvements include:

- Alkaline models get double the battery life of their predecessors, so you can spend less time and fewer resources replenishing your power supply and more time recording wildlife and soundscapes.
- A tougher, IP67-rated weatherproof housing that is built to withstand the most rugged terrestrial environments, so you can deploy confidently, knowing your recorders are proven to perform dependably in harsh elements.
- A redesigned, hinged, lockable enclosure makes it easy to gain (and prevent unauthorized) access to your recorders, freeing up your hands to focus on deployment without worrying about a separate lid.
- An added tripod mount enables flexible deployment in a variety of habitats using off-the-shelf equipment.

 

What are the differences in recording quality between the Song Meter SM4BAT FS and the Song Meter Mini Bat?

The Song Meter Mini Bat is built with the same microphone element used in our SM4BAT FS ultrasonic microphone, the SMM-U2. In many recording scenarios, the recordings produced by an SM Mini Bat will be nearly identical to those produced by a Song Meter SM4BAT FS paired with an SMM-U2. However, the SM4BAT FS uses more advanced recording and trigger circuitry that gives it an edge over the SM Mini Bat.

For unattended bat recorders like our ultrasonic Song Meters, the ability of the recorder to detect a passing bat and start recording is as important as the quality of the recordings it produces. Both the SM4BAT and the Mini Bat use adaptive triggering. The recorders are listening for ultrasonic sounds loud enough to be detected through the general noise level of the surrounding environment. When they detect a loud-enough sound in this range, they start recording until that sound is no longer detected. There is a difference, however, in the type of triggering the records employ. The Mini Bat (like almost all other bat detectors on the market) uses a broadband trigger where the bat has to exceed the background noise across the ultrasonic spectrum. The SM4BAT-FS uses a narrowband trigger breaking and splits the frequency range up into many narrow bands, monitoring each band separately. When a sound is detected in any of the bands in the user-specified trigger frequency range, The SM4BAT starts recording. What this means is that if there is persistent background noise in some portion of the ultrasonic spectrum, such as from insects or nearby electronic equipment, the SM Mini Bat’s trigger sensitivity will be affected by that background noise, regardless of its vocalization frequency range. In noisy environments, the SM4BAT FS will tend to produce more bat recordings than the SM Mini Bat.

 

What types of AA batteries are compatible with the Song Meter Mini and Song Meter Micro families?

The following Song Meter recorders accept AA batteries:

Current products:
- Song Meter Mini 2 (AA)
- Song Meter Mini Bat 2 (AA)
- Song Meter Micro 2

Legacy products:
- Song Meter Mini
- Song Meter Mini Bat
- Song Meter Micro

Several different types of AA batteries are commonly available:
- Alkaline
- Nickel-metal hydride (NiMH)
- Lithium iron disulfide (sometimes labeled “Lithium” or “Ultimate Lithium”)

We strongly recommend using alkaline batteries for the most consistent performance.

Alkaline
Alkaline batteries are the most common type of single-use AA batteries. When using AA batteries, the Song Meter Configurator app assumes you are using high-quality, alkaline batteries at room-temperature conditions when estimating run time or providing a battery life percentage.

We have found Energizer alkaline AA batteries to perform very well.

Nickel-Metal Hydride (NiMH)
NiMH batteries are the most common type of rechargeable AA batteries. If you only need to deploy recorders for short lengths of time and want to throw away fewer batteries overall, NiMH batteries can be a good option. However, if you use NiMH batteries with a Song Meter, be aware of the following:

- NiMH batteries will typically last 50-70% as long as alkaline batteries before needing to be recharged. This battery life will decline as the batteries are used and recharged repeatedly.
- Different brands and models of NiMH batteries have different capacities. This is often advertised as a charge capacity, measured in milliamp-hours (mAh).
- The battery percentage readout in the recorder's Status screen will read lower than the batteries' actual state of charge. This is because NiMH batteries run at a lower voltage than alkaline batteries. For example, when the batteries are fully charged, the Status screen may only read 90%.
- NiMH batteries will die much more quickly than the Song Meter Configurator's battery life estimations. Even though the battery percentage is underestimated, the total lifespan of NiMH batteries is significantly shorter than that of alkaline batteries.

Lithium/Iron Disulfide
Lithium iron disulfide batteries are sold under multiple brand names, including the following:
- Energizer Ultimate Lithium
- Ansmann Extreme Lithium
- Ansmann Industrial Lithium

Lithium iron disulfide batteries should not be confused with lithium-ion batteries, which are generally not available in AA size.

Lithium iron disulfide batteries primarily benefit devices that draw much more power than Song Meters, but they can outperform alkaline batteries in freezing temperatures. However, if you use lithium iron disulfide batteries with a Song Meter, be aware of the following:

- The battery percentage readout in the recorder's Status screen will read higher than the batteries' actual state of charge. This is because lithium iron disulfide batteries run at a higher voltage than alkaline batteries. For example, if the Status screen says the batteries are at 60% life, they may actually be at 10% life.
- Because the battery percentage is overestimated, the Estimate battery and card life window in the app will also overestimate how long partially-used batteries will last before depleting.
- At the very end of the batteries' life, the Song Meter may lose and regain power several times before fully shutting down. This can result in several unusual behaviors:
The Song Meter may produce truncated, unreadable, or “0 KB” recordings at the end of its deployment.
The Song Meter may produce multiple diagnostics (.minidiags) files at the end of its deployment.
The SD card may be marked “dirty”, meaning you must connect it to a computer before using it to record again.
In rare cases, the SD card may become corrupted, meaning you must run a repair or recovery tool in order to recover your recordings.

 

Can I copy a schedule from one Song Meter Mini to another?

If you have multiple Minis of the same type (i.e. all Minis or Mini Bats) and the same microphone configuration, you can use the Mini Configurator app to configure a schedule and settings to be used on several Mini recorders. You can either send the configuration file to a computer for transfer onto SD card and then load the configuration onto the Minis form the card. Or you can pair your mobile device to the Minis one at a time and transfer the configuration. Additionally you can send the configuration file to another user via email or text and they can import it into the Mini Configuration app on their device for transfer to their Minis.

 

Does power consumption change based on what type of microphone or how many microphones I'm using?

If you are using a Mini with two acoustic microphones connected, recording on both microphones simultaneously will use between 5% and 20% more power than recording on a single channel at a time. When you are planning your deployment, the Mini Configurator app will take this into account when estimating how long your batteries will last.

 

Can I connect the Song Meter Mini (Bat) to an external battery?

No. The first- and second-generation Song Meter Mini and Song Meter Mini Bat do not support external batteries.

However, the following models support up to six 18650 lithium-ion batteries, allowing for internal battery runtimes longer than any previous Song Meter model:

- Song Meter Mini 2 Li-ion
- Song Meter Mini Bat 2 Li-ion
- Song Meter Mini 1, with Li-ion lid accessory
- Song Meter Mini Bat 1, with Li-ion lid accessory

Using six lithium-ion batteries and standard settings, these models can record 1,330 hours of audible sound, and the Bat recorders can monitor up to 125 ten-hour nights.

For even longer deployments, the Song Meter SM4 and SM4BAT FS recorders support external power from the Wildlife Acoustics Power Kit or third-party power sources.

 

Can I run the same schedules on the Song Meter Mini as I do on my SM3 or SM4 series recorders?

The Mini uses the same schedule block system as the SM4's default daily scheduling mode. This allows you to very easily set up complex schedules that repeat on a daily basis. Recording segments can be timed with reference to a specific time on the clock or based on an offset from local sunrise or sunset. Unlike the SM3's programming system and the SM4's Advanced scheduling mode, the Mini cannot be programmed to run different schedules on different days. This may be added in the future.

If you are using a Mini Bat with both the built-in ultrasonic microphone and an optional acoustic microphone, individual schedule blocks can be set up to record either ultrasound or acoustic frequency sounds at different times of the day. For example, you could program a single Mini Bat to record birds during the dawn chorus, plus several short recording periods during daylight, then automatically switch to triggered ultrasonic recording for bats after sunset. It is not possible to record from both the ultrasonic and acoustic mics simultaneously.

 

Can anyone with a phone or tablet access my Song Meter Mini?

By default, the Mini will broadcast Bluetooth beacons roughly once every ten seconds. Any person within 20 meters with the Mini Configurator app installed on their phone or tablet will be able to view basic info about the recorder, including its name, serial number, and the state of its SD card and batteries. In order for changes to be made to the recorder's settings from a phone or tablet, a physical button on the Mini must be pressed to pair the recorder with the phone or tablet.

Optionally, the Mini Configurator app can be used to turn off the recorder's Bluetooth beacons. When beacons are turned off, no mobile device will be able to receive status information from the recorder unless a physical button is pressed to pair it with a phone or tablet.

 

Do I need a smart phone or tablet to use the Song Meter Mini?

While some basic functions, such as importing a schedule or firmware update from an SD card, can be done without pairing the SM Mini to a phone or tablet, full use of the device requires an iOS or Android device with Bluetooth version 4.0 or later. During the deployment, a phone or tablet can be used to check the status of the Mini from up to 20 meters away.

Before deploying the recorder for the first time, you must update the SM Mini's internal clock by pairing the recorder with the app. When you change the batteries, or if the batteries die, a rechargeable internal battery will keep the SM Mini's clock running for about a month until the primary batteries are replaced. If the primary batteries and clock battery die, you will need to pair with the recorder again to reset the clock before you can continue recording.

 

Can I transfer recordings to my phone over Bluetooth?

The Bluetooth functionality is limited to making setting changes and checking the recorder's status. Transferring recordings would be very slow and deplete battery life significantly. Recordings are saved to an SD card for fast and easy transfer to a computer.

 

What is the Song Meter Mini’s Bluetooth range?

The Mini can communicate with a phone or tablet over Bluetooth at an effective range of up to 20 meters/65 feet without obstructions (this varies widely across different devices and in some cases, depending on what device you are using, you may need to be much closer). The Mini does not have the ability to communicate over long-range networks like Wi-Fi or Cellular.

 

What SD Cards Should I Use With My Recorders?

Brand
We have found SanDisk cards to be the most reliable with all Song Meters. PNY and Kingston cards also work well.

Regardless of the brand you use, ensure that it is from a reliable electronics seller. Counterfeit cards are commonly sold on platforms with many third-party sellers and are more likely to malfunction than genuine cards.

Speed Class
Currently, all new SD cards produced by major brands are fast enough to be used with a Song Meter. Faster cards may allow you to back up your data to a computer more quickly, but the Song Meter itself does not benefit from a faster card beyond its minimum requirements.

If you plan to use older SD cards, make sure it has a speed class marking that matches at least one of the following:
- C4, C6, or C10
- Any "U" speed class
-Any "V" speed class

Capacity: SDHC and SDXC
SD and microSD cards with a capacity between 4 GB and 32 GB are classified as "SDHC", while cards between 64 GB and 2 TB are classified as "SDXC."

Our oldest Song Meter recorders, the Song Meter SM1, SM2, SM2+, SM2Bat, and SM2Bat+, only support SDHC cards. Using SDXC cards with these recorders can result in missing audio.

All of our more recent Song Meters support both SDHC and SDXC cards. This includes the following models:

Song Meter SM3 and SM3Bat
Song Meter SMZC
Song Meter SM4, SM4BAT FS, and SM4BAT ZC
Song Meter Mini, Song Meter Mini Bat, and Song Meter Micro
Song Meter Mini 2, Song Meter Mini Bat 2, and Song Meter Micro 2

 

What Does It Mean When An SD Memory Card Is “Dirty”?

If a Song Meter series recorder detects a problem with an SD card, it will mark the card as "Dirty" and no longer record to that card in order to avoid corrupting any further data.

This can happen if a recorder momentarily loses power or if the batteries drop below the voltage required to power the recorder.

If a Song Meter runs a recording schedule until the batteries are depleted, it is likely that the SD card(s) will be marked dirty at the end of the deployment. This is completely normal and should not cause alarm. There may also be empty .wav files at the end of a deployment when power is lost during recording.

On Windows (and other operating systems), when inserting a "dirty" card, the operating system should either automatically check and repair or prompt you to check and repair the card. This is almost always recoverable and your data should be preserved.

Dirty cards can be used again after they are formatted, either using the Format Cards utility on the Song Meter recorder, or by using the SD Association Formatter.

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