Here's an oscillator circuit that doesn't use the Speaker or Earphone, you don't hear Its output. Instead, you see the output on a LED.
This Project will give you an idea of how large strobe lights work. Put power ON and watch LED 1. You'll see it light on and off at a certain interval. You can control the rate at which LED 1 "blinks" with the 5OK variable resistor. This Project lets you get a "bird's eye view" of how an oscillator works.
The charging and discharging of the 100 uF capacitor controls the rate at which the LED ''blinks". Try substituting a lower value capacitor and see what happens to the "blinking" rate.
This Project also shows you another advantage of LEDs over ordinary light bulbs like the Lamp. A LED can light on and off faster than the Lamp (we say it has a faster response time). LEDs also use less current, don't give off as much heat and last longer than ordinary light bulbs. That's why you see LEDs in more and more electronic devices these days.