SONG METER COMPARISON

The Signal to Noise Ratio (SNR) is a measure (as a ratio expressed in dB) of a reference signal against the background noise. This is typically relative to a 1 Pascal (= 94dB SPL) signal at 1kHz as compared to the recording system (microphone and electronics) self-noise.

A higher SNR implies that the recorder can detect quieter signals at a greater distance before the signal is lost in the noise.

Every additional 6dB of SNR doubles the distance at which a signal can be detected, assuming no environmental background noise such as wind, rain, road noise, or airplanes.

A recorder may have higher or lower relative SNR at different frequencies. The SNR Chart below can be used to assess the signal-to-noise ratio and its impact on recording the frequencies of specific species. For example, the Micro has a particularly good SNR at just under 6,000 Hz so it would record better around that frequency.

In the Song Meter family, the SM4 has the best overall SNR followed closely by the Mini, and then the Micro.

The Frequency Response curve shows the sensitivity and noise of a recorder across its frequency range. The flatter a frequency response curve, the more accurately a recording represents the signals recorded. Frequencies at peaks or troughs in a curve will be relatively over or under recorded, giving a louder or quieter signal.

Note that frequency response can be affected by other factors such as the angle of the sounds as they hit the microphone and interference from trees or other structures to which the recorder is mounted.

The Sensitivity Chart below can be used to assess frequency responses for the Song Meter family. The SM4 has the flattest frequency response followed by the Mini, and then the Micro

A High-Pass Filter (HPF) reduces the amplitude of lower frequency signals (like those caused by wind, rain, vehicles, or airplanes) while allowing frequencies above a certain frequency to pass though. This can reduce audio distortion in the recordings caused by lower frequency sounds that are too loud for the microphone to handle.

In the Song Meter family, the SM4 offers the greatest flexibility, with a high-pass filter that can be set independently on each of its two channels to optimize for different conditions and species of interest. It can be set to off (no high pass filter), 220Hz, or 1000Hz. The Mini and Micro have a fixed 100Hz high-pass filter, meaning that it filters out sounds below 100Hz. Therefore, if you are recording in the infrasonic range, the SM4 may be a better solution since the high-pass filter can be turned off.

An Anti-Alias Filter reduces aliased signals in the recording. Aliasing is an audio artifact that occurs when high frequency sounds are recorded that are above half the chosen sample rate. When this happens, part of the higher signal appears in the recording as unwanted noise. You can see a visual example of this here.

In the Song Meter family, the SM4 offers the strongest anti-alias filter, reaching 55dB of signal reduction at 60% of the sample rate. The Mini has a weaker anti-alias filter reaching only 12dB of signal reduction at 60% of the sample rate. The Micro has the weakest anti-alias filter reaching only 6dB of signal reduction at 60% of the sample rate.

Adjustable Gain allows flexibility to choose the optimum setting for any deployment. Gain makes a signal louder when it is being recorded. However, too much gain can cause loud signals to clip, resulting in distortion and too little gain may result in a poor resolution and a lower quality recording.

The SM4 offers the greatest flexibility with a 26dB gain pre-amplifier and additional gain of up to 59.5dB in 0.5dB increments. The Mini and Micro offer 4 gain settings in 6dB increments between 6 and 24dB