what I'm searching for are voice samples where a single person says something unintelligible (like in The Sims) or simply noises like "hum", "oh?".
How could I come up with something like this in my game?
I'll state the obvious: You can record it. Welcome to the world of voice acting.
Simlish was improvised by voice actors.
With that said, if I can get you interested in a system to generate and play the audio, I would like to separate the problem in two dimensions:
- When to play the sounds.
- What sounds to play.
When to play the sounds
Many old RPGs played a sound per character of the text. Usually at the same time the character is revealed on the screen. Beyond that, you are going to add a burden to any translation effort.
For example, you could hyphenate the text, and have a sound per syllable.
Or, for something more elaborate, you could convert the text into phonemes and play a sound per phoneme.
What sounds to play
Those same old RPGs used simple beep sounds (sine waves) with pitch variations.
One step above that is to have a wave generator that can generate random effects and use it instead of the beep sounds.
Alternatively, you could have grunt style audio samples and play them with pitch variations (Take Banjo-Kazooie for inspiration). Or use music instrument samples (Take Don't Starve for inspiration).
And, of course, you could have multiple gibberish samples. For example you could have specific samples for specific texts (phonemes, syllables, words…), except they do not match the text pronunciation, but there would be a one to one mapping between audio and text (at least in one language). You could also have variations of them for end of sentence, questions and other intonations you may want, or you could handle that with pitch variations.
I have found a few things that you could be interested in:
- sfxr: This is an 8-bit style sound effect generator (this one has been ported many times, so you may want to search for a port for either the audio tools you are using, or the game engine you are using if you want to generate the effects in real time).
- RPG Dialogue Generator: This is a Unity asset phoneme based gibberish audio, also inspired by Animal Crossing speech.