This article from Tzomet is mainly focused on the use (non-use) of microphones on Shabbat. Within it, he cites the Talmud Shabbat source and explains:
According to Rashi, mashmi’a kol does not belong to the category of
melacha, but is rather for*bidden because it constitutes a sort of
“weekday activity”(uvdin d’chol) and “denigration of Shabbat”
(ziluta). So too wrote the Meiri: “This act creates noise and is
widely known, which constitutes disrespect for Shabbat; but some
permit even this.” In light of this, any activity which creates loud
noise should be prohibited, due to disrespect for Shabbat. And in
fact, this approach is quoted by the Darkei Moshe in the name of
Mahari Weil: “One is forbidden to set on Erev Shabbat a clock
[apparently a “grandfather” clock] which will make a loud noise on
Shabbat, due to hashma’at kol.”
However, the Darkei Moshe also quotes the Agur, who permits setting a
clock before Shabbat: “This is not similar to the sound of a water
mill, since one hearing the noise of a water mill on Shabbat will
think that the owner placed the grain in the mill on Shabbat itself;
whereas regarding clocks, everyone knows that they are set the day
before, and are not set on the day they chime.” According to this
approach, the entire problem is that others will think that a
forbidden action was performed on Shabbat.
The difference between these two approaches (namely, whether
hashma’at kol is forbidden due to disrespect of Shabbat or the
impression that a prohibition was violated) is expressed in a case
where a loud noise is created, but it is clear that no prohibition was
violated (such as the case of the grandfather clock).
The above is an excerpt. There are various opinions cited in the article.
Activities that I am aware of (based on my learning about this from local Rabbanim) are:
Using a microphone (among other reasons)
Leaving the radio / T.V. on when set on before Shabbat or on an alarm clock (varying opinions on this. See this article)
Using a regular alarm clock (buzzers, bells, whistles, etc. - also varying opinions)
Running a washing machine or dryer just before Shabbat so that it runs during part of Shabbat
Leaving a tea kettle on a blech. (Assuming the water wouldn't boil out, of course - safety issue - burning the kettle, which would set off your smoke alarm - possible hashma'at kol :-) :-) )