Tech Tip Thursday from Facebook
The human ear can hear a range of audio frequencies from approximately 20 - 20,000Hz (20 - 20KHz). When selecting an audio recorder, the closer it comes to being able to record this full range of frequencies, the better the resulting quality will be and the less likely you are to miss EVPs that are subtle whispers.
Many smaller recorders are optimized for recording the human voice. They intentionally restrict the frequency range to a narrow frequency band around where we speak. This allows them to record longer at the expense of a larger range of recorded frequencies. Whispers contain frequency components above the normal spoken range, and might be missed by a recorder designed this way.
This doesn't mean that these voice recorders are "junk" or were designed poorly. They were designed for the purpose of recording the human voice for meetings, dictation, note-taking, etc. They were not designed with paranormal investigation in mind.
Another component that is often overlooked in these recorders is the microphone itself. Many times, in the interest of size and cost, lower-quality microphones (suitable for voice reproduction) are selected. These further complicate the frequency reponse problem when recording.