It is disputed whether soda/seltzer makers are a problem on Shabbos (see Making seltzer/soda water on Shabbat or Yom Tov ) with e.g. the Shemiras Shabbos K'hilchasa ruling leniently (as cited in Rabbi Dovid Ribiat's "The 39 Melochos").
The focus in these works seems to be primarily m'leches makeh b'patish (completing) (and/or uvda d'chol [weekday activities]). Is there an explicit discussion in the poskim, with regard to soda-makers, of the issue of molid (creating something new; a la, e.g., the Rabbinic ban on infusing clothing with incense smoke)?
Also, the instructions (at least on the SodaStream sodamaker) make explicit use of the sounds created by the device to determine when the seltzer is ready (e.g. "press the carbonating button several times until you hear the LOUD BUZZ that indicates carbonation"). Do poskim address whether this is a problem of the Rabbinic ban on hashmaas kol (making a noise)?