<p>Acoustic studies are usually carried out using sound level metres and acoustic frequency analysers, which are classified and standardised according to international standards. However, some acoustic assessments cannot be carried out using conventional sound level metres and spectrum analysers, due to the need for covering large surfaces and many monitoring points, the requirement of simultaneously using numerous devices, the high cost derived from leaving these instruments outdoors, or their short autonomy. Moreover, in recent years, many authors have begun to use small digital recorders and even mobile phones for acoustic analysis. These devices are small, cheaper, and quite versatile and greatly autonomous, which make them appropriate for those acoustic studies where sound level metres are not the best option. The methodology presented in this paper proposes the use of small digital recorders and WAV file post-processing software to replace the use of sound level metres and spectrum analysers, obtaining results with a precision comparable to that of a Class 1 sound level metre and acoustic analyser.</p>