Many of the sound level meters and noise monitoring systems have outputs so that you can develop an interface to integrate with your own recording or monitoring system. The common interface methods are listed below, some of which are available as outputs from sound level meters with others as outputs from noise processors or noise warning signs.
The latest addition to the range of meters for system integration is the NoiseAPI range. These units measure and store the sound levels, analyse the noise and present the results via an API. Your application can access the noise measurements using HTTP or HTTPS requests and live feeds of sound level can be accessed using WebSockets.
For recording the audio or if you need to carry out detailed acoustic analysis (FFT for example) then you need to use a sound level meter with an unweighted AC output. If you are running a simple data logging system that can accept a DC level, which can be easily converted to dB, then the DC voltage option is better and you just need to consider the physical aspects - hand held meter, noise processor or wall mounted noise warning sign.
The 4-20mA current loop output from the noise processor and noise warning signs is ideal for integration with many process control systems. It is also better than the DC voltage option when dealing with the resistance of longer cabling. For IoT development, web applications and other software applications the Noise API is the best approach.