Audio Recording Method
In my our audio research, we use different search methods and devices like radio, ghost box, landline and cell phones and digital recorders. The audios captured are analyzed in the Audacity program (https://www.audacityteam.org).
The Ghost Box (ver Equipamentos para a Gravação de Áudios) is a common radio, modified so that the stations change constantly and rapidly, "sweeping the radios", creating a mixture of white noise and other sounds, thus facilitating the formation of voices.
We currently use two recording methods. The first is simply to record using the Ghost Box as the source of background noise directly in the Audacity program, through the microphone built into the computer or the electro-magnetic microphone . The Ghost Box can be replaced by a common short-wave, out-of-sync radio (white noise).
In the second method, we also used the Ghost Box as background noise, but we recorded through a landline and a cell phone. First, we call from the landline to the cell phone. The cell phone is next to the computer, with the speaker turned on, amplifying the volume and generating more noise. We put the landline phone next to the Ghost Box in another environment, turned on and scanning FM radio. The Audacity program records audio from one phone to another through the microphone.
The use of these devices only facilitates the hearing and helps in the subsequent analysis and understanding of the messages, but does not determine or guarantee the contacts.