Phantasm and Trid Phantasm say they are visual illusions, and there isn't any spell in the SR3 or MITS that produces the illusion of sound except for Physical Mask which affects only the target's voice. Is this an oversight or is it not possible to create a full visual and auditory illusion?

Like the SR3 Phantasm descrip. talks about a fire-breathing dragon illusion and that would be -10% believeable were there nil sound.

Actually, there's good evidence that both Chaos and Confusion (and Chaff and Flak) generate auditory effects as part of their attempt to drive the target to distraction. And, according to the spell-design examples in MitS, the Phantasm spells are multi-sense illusions - hence D-level drain and description as 'realistic', I suppose. It's kinda confusing why it still says that the Entertainment family are visual-only. The rest of the description says that they're used to "create new and interesting sensations", including those that aren't physically possible. As SR has functioning open-air holograms, I don't quite see how a free-standing silent image really fulfills that promise.

But, yeah, it seems there are no strictly audio illusions written-up in the books. Well, both Silence and Stealth are auditory in nature, as is Sound Barrier - though, admittedly, they make the illusion of no sound, rather than a particular noise. However, there's nothing preventing one from designing one with the rules in MitS. Heck:

Whispers
Type: M
Target: W
Duration: S
Range: LOS
Drain: L
Class: Illusion (direct)

This obvious, auditory illusion spell allows the caster to be heard by the target, regardless of distance or ambiant noise levels. The caster can speak in normally-audible tones or sub-vocalize and the target will hear their words as clearly as if the caster were speaking directly into their ear. Though it doesn't allow for direct two-way communication, the spell lets those who would otherwise not wish to be heard (whether invisible or otherwise attempting to avoid detection) communicate with their teammates without the possibility of being overheard.

You're right, in MITS it does reverse-engineer Phantasm as "multi-sense" in the example, yet in SR3 it says "creates convincing visual illusions" making it sound single-sense. I've always naturally considered it multi-sense until I read the description carefully.

You're also right about Confusion spells, etc. creating sound--what I meant to ask about was spells that create sound to the creative whim of the caster instead of as a randomized distraction. I like the Whisper spell.