Audio designers exist for a reason. In the past, with severe hardware limitations, sound was often left for simple sounds with no care taken about creating immersion, depth, conveying emotions, etc. That's no longer the case with games using complete soundtracks with great care taken to convey emotions. The same discussion about contrast, intensity, ambience, etc that is made with light and textures applies to sound as well. After all, both light and sound are waves that obey to the same physics. The most important difference is that light is much faster than sound and with the exception of deaf people, light takes precedence over sound.

Hourences makes a distinction between ambient and detail sound. The former is sound that doesn't have a clear or visible source, such as wind or creaking sounds from large constructions. The latter are sounds with clear and visible sources such as waterfalls, machinery or animals. Whenever you can, put those sounds in your level because they add depth and help create a more living world. I'd add that there is an issue here related to the propagation of sound. With light the hard part is adding indirect light because it's incredible expensive to calculate it. With sound old games tend to completely disregard occlusion, meaning that sounds propagate through geometry with no calculations performed in regards to absorption and transmission.

There isn't much in the book about sound. The most basic discussion that book makes is about the importance of variation. We can easily recognize when multiple sounds are exact copies of one another because the repetition is an easy pattern to recognize. In here we also have a technological limitation because there isn't enough memory or processing power, or human resources, to produce unique sounds for everything.

In the same way there can be excessive contrast of light, we can have excessive contrast of sound. Too many different sounds playing at the same time is confusing. And they can also have an unwanted additive power, making the environment too loud. In the real world we have to turn off machines, remove animals from the place or stop the water flow to turn off the sound. In games we have the luxury to have control over sound, light, behaviours and geometry all separated from one and another. Take advantage of this.