If you don't need the ultimate in sound quality or volume, a much simpler approach is to use the prop shield instead of the audio shield.
The prop shield has the following features:
- It has flash memory to store the thunder effect. Note, if the effect is small enough, you can put it in program memory, but often times your sound effect is larger than can fit in the available memory. The 3.6 has more memory than the 3.2, so you might be able to store the sound in the 3.6 directly. In addition, the 3.6 has a built-in micro sd-card, so you could put the sounds on the card. To use the flash memory, you would need to download files to it (there is a sketch that does this).
- The prop shield has a built-in mono amplifier. So for a Teensy 3.2, all you have to do is connect up an small speaker. For the 3.6, you would need to run a wire from A21 (DAC1) to the back pin where A14 is on the 3.2.
- The prop shield has built-in level shifters for the WS2812B (neopixel) or APA102 (dotstar) leds. There can be problems if you use SPI displays and want to do the pixels at the same time (you have to switch pin 11 and 13 from SPI mode to normal mode and back).
- The more expensive of the two prop shields has a motion sensor in it, so you could activate the effect by moving it.
Using either the prop shield or the audio shield should work. If you use WS2812B (neopixel) LEDs, if you have a lot of LEDs, it can be somewhat tricky if you are playing sounds when doing the LEDs. The WS2812B LEDs have a strict timing window, so the default libraries turn off interrupts while doing the LEDs. Unfortunately the sound system uses the interrupts to keep the music playing, so you might hear a choppy output, if the interrupts are held too long.
If you are just playing a single effect, a simpler approach might be to get a DFPlayer (
https://www.dfrobot.com/product-1121.html) which has a micro SD card, and you can use either Serial commands or pins to get it to play MP3 or WAV files. This way you don't have to do all of the sound programming in the Teensy (unless of course you want to learn how to do it). Note, the DFPlayer has been widely cloned. It may make sense to get the original one from dfrobot.com.
I picked up a thunder .WAV file from
http://www.hauntedbay.com/downloads/sounds/ many years ago, and it seems to still be there. Now, whether they legally have permission to distribute the copyrighted material (like Monster Mash, This is Halloween, Ghostbusters theme song, etc.), I dunno.