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 four 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.
A DC voltage that is proportional to the frequency weighted dB level, usually dB(A).
The current is proportional to the frequency weighted sound level, usually dB(A).
The raw signal from the microphone, amplified and unweighted or Z-weighted.
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. And finally the trusty RS232 interface is still available, with the CEL63x series sound level meter set up to automatically send periodic noise measurements as they become available. With these measurements sent over the RS232 connection in a simple text format, decoding should be relatively simple.