Weather V+ Design

feature author: Paul Halliday

The Weather worksheet, Figure 28, has three models:

1. Thunder

2. Rain

3. Hail

The Thunder model is pretty simple. It has two players, one for the rear speakers, and one for the sub-woofer. The frequency, balance, and enable pins are hard-coded constants. The volume for the players is turned to maximum when the thunder input is turned on at the host. Pretty simple, huh? The WAVE file that is played is a pretty long one that continues to repeat, giving it the “appearance” of random thunder.

The Rain and Hail models are the same except for the inputs that they receive, and the WAVE files that they play. They both have two looped players, one for the front speakers, and one for the rear speakers (using the sub-woofer would have no effect as these sound files have a frequency domain higher than the sub-woofer could play). The balance and enable input pins for the players are constants.

The volume for these players is a function of rain/hail intensity. These inputs go to a 1st Order Low Pass Filter object which smoothes any abrupt changes coming from the host. The output of the low pass filter is then fed to the LFI shown in Figure 26. The curve shows us that it’s going to get loud pretty quick.

The frequency for the players is a function of air impact pressure. As the air impact increases, so does the frequency, as shown in Figure 27. This makes sense, doesn’t it? Take for instance driving in your car while it’s raining moderately. When you come to a stop, there’s not much noise from the rain or hail hitting your windshield. When you’re going say 50 mph, more rain or hail is going to hit your windshield.

Figure 28.  Weather Design