About 40 years ago, I built a bird sound kit and put it in a Sucrets® metal box (same size as an Altoids® tin). I don't remember the name of the company, but the circuit was a blocking oscillator. I believe it had a miniature audio transformer; one side had a center tap. I think it only had one transistor and ran on a single AA cell. I used a 1" speaker with a clear plastic diaphragm. You switched it on and it made a realistic repeating bird chirp. Better yet, if you lightly touched the speakercone, the sounds changed to other types of birds because of the change in reactance of the speaker. It was quite loud. Does anyone remember this and have a schematic?
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The schematic and parts list shown below is from the three page article “The Solid-State Bird,” by John Simonton, Jr. It appeared in Popular Electronics Spring 1973 “Electronics Experimenters Handbook.” (A scanned PDF of the entire article can be viewed or downloaded here also.) The foil pattern measures 2 7/16" x 1-3/4", or 71 x 44 mm. While searching, I also ran across two additional "bird sound" circuits: Dec. 1981 Radio Electronics "Electronic Bird Chirper" — four transistors, total 25 parts; and 1993 Popular Electronics Electronics Handbook "Hot Canaries" two LM324s, one transistor, two 1N914 diodes total 54 parts (no critical parts; parts count includes 9V battery, switch, and speaker).
I remember using a SN76488N 'sound generator' to build 'sound' circuits, such as train whistles, crowds cheering, birds chirping, and sirens, etc., for electronic games and other projects, but then I started to think about producing sounds as realistic as possible but in a less complicated way. Here's a possible solution that you might want to consider. I went to RadioShack and purchased a few of those handheld voice recorders [available at www.tmart.com] that allowed about a 10 to 15 second recording time. Pressing one button allowed recording, and pressing another button allowed audible playback. Removing a few screws, I simply wired a micro-switch in parallel with the playback switch and, when pressed, could instantly and repeatedly hear what I had recorded until I recorded over it with something else. I wired the output of the recorder to the input of a small audio amplifier [using an LM386 IC circuit] for a clear and loud output. I wanted a crowd cheer each time a hit was made and a trumpet blare every time a man crossed home plate in my electronic baseball game. I was fortunate enough to have these realistic recorded sounds already programmed on my Technics keyboard. I simply pressed the record button, recorded the sounds, and then wired the recorders into the game. You can easily record real bird sounds for your project. You can store all bird calls into a memory chip and then play back, record, and use as needed.