Added Info MODERN ELECTRONICS [2] Jan 1986 (v.3#1) pg. 5
Sound-level meter incorporates a visual LED bar graph readout with a range of 30 to 120 dB. Est. cost: $48 (kit).
POPTRONIX HOBBYISTS HANDBOOK Winter 1996 pg. 55
"Riot Restrainer". Alarm sounds when noise exceeds a predetermined level, turns off when noise level goes down.
POPULAR ELECTRONICS [1] Apr 1969 (v.30#4) pg. 47
Listen to a new world of sounds with an ultrasonic detector. This inexpensive detector converts ultrasonic sounds from insects, compressed gas leaks, small animals, etc. into an audio output.
POPULAR ELECTRONICS [1] Jul 1978 (v.14#1) pg. 64
Electronic "knock detector" helps trace down the source of strange knocking noises in electro-mechanical devices, such as automobile engines.
POPULAR ELECTRONICS [2] Aug 1989 (v.6#8) pg. 81
Sound-level meter circuit uses LED's to indicate sound levels from 65 dB up to 115 dB or more. Four sensitivity ranges are controlled by a rotary switch.
POPULAR ELECTRONICS [2] Oct 1989 (v.6#10) pg. 84
Fun with op-amps. Part 2. (1) Operation and theory. (2) Telephone amplifier circuit for hearing impaired or noisy environment. (3) Audio alarm sounds a buzzer when the noise level gets too high.
POPULAR ELECTRONICS [2] Feb 1992 (v.9#2) pg. 68
Build a sound-level meter with a dynamic range of 30 to 120 dB. Est. cost: $48 (kit).
POPULAR ELECTRONICS [2] Nov 1995 (v.12#11) pg. 56
Patio alert. A wireless receiver which can be activated by three transmitters which in turn can be activated by anything that makes a noise (doorbell, telephone, baby crying, etc...). House wiring carries signal. Receiver buzzes and turns on a light indicating source of noise.
POPULAR SCIENCE Apr 1972 (v.200#4) pg. 115
Circuit monitors sound level and lets you know when it rises above or falls below a predetermined level.
RADIO-ELECTRONICS Jan 1980 (v.51#1) pg. 68
A circuit which will generate a direct-current voltage whenever a radio loudspeaker is activated. Use the circuit as a form of "sound" detector to control some other device.
RADIO-ELECTRONICS Jul 1983 (v.54#7) pg. 77
Detecting signals with noise. Exploring the phenomenon called "stochasic resonance" where electronic noise can boost an otherwise weak signal above the threshold of detection. Requires the construction of a threshold detector circuit, noise module circuit, and signal module circuit. Est. cost: $100.
SCIENTIFIC AMERICAN Aug 1995 (v.273#2) pg. 100
Sound level meter incorporates the Panasonic omnidirectional electret condenser microphone.
SPEAKER BUILDER 1/1986 [Apr 1986] (v.7#1) pg. 34
Correction SPEAKER BUILDER 2/1986 [May 1986] (v.7#2) pg. 44
Converting Radio Shack's sound level meter to also function as a millivolt (mV) testmeter to measure loudspeaker response.
SPEAKER BUILDER 4/1994 [May 1994] (v.15#4) pg. 12
Correction SPEAKER BUILDER 6/1994 [Aug 1994] (v.15#6) pg. 53
Correction SPEAKER BUILDER 5/1995 [Jul 1995] (v.16#5) pg. 68