A speech processing device initiates the turn on of a yellow or a red light once the background noise exceeds the corresponding thresholds set by the impaired child through the use of a wireless keychain. The lights will turn off once the background noise descends below the thresholds.
A band limiting low pass filter, a microphone, and a signal conditioning circuit will provide an electrical signal pertaining to the background noise generated within the classroom.
The signal is processed by a PIC (programmable chip) which determines whether or not the preset noise level threshold has been exceeded or not.
The impaired child can at any time increase or decrease the noise thresholds for the red and yellow lights by pressing one of two sets of buttons corresponding to each light.