Left side can be solar cell, LED, or GaAs:Si near infra red ( about 940 nanometer light range). Right is plug in to amplifier's input jack. Adjust volume from low to high.
Solar cell can detect electrical storms you cannot see and pinpoint peak areas of electrical storm activity.
Detectors can let you hear " chime" sound when you tap light enough to vibrate filament. Hear light patterns of campfire. Light source behind hummingbird or flying insects, point at sun and walk behind a picket fence, or pick detector for narrow wavelength responses to hear buzz of fluorescent lamps. What light patterns interest you?
