The letter `Ĝ`/`ĝ` is rendered in IPA (the [International Phonetic Alphabet](https://en.wikipedia.org/wiki/International_Phonetic_Alphabet)) as `d͡ʒ`.  This is the sound most English speakers make when pronouncing the `g`s in the English word `ginger`, and the `g`s and `j`s in `Giant Gene gingerly jumps joyfully`.

The letter `Ĵ`/`ĵ` is rendered in IPA as `ʒ`.  This is the sound most English speakers make when pronouncing the final `g`s in the English words `garage` and `mirage` (although you could argue that those words are derived from French).  (Note that the word `garage` has two `g`s; the first is like the Esperanto `g`, the second is like the Esperanto `ĵ`.)

The `s` in the English words `measure`, `pleasure`, and `treasure` also matches the sound of the Esperanto letter `Ĵ`/`ĵ`.  So the letters `g` and `s` make the sound of Esperanto `Ĵ`/`ĵ` in this sentence:  `That treasure ain't no pleasure -- but a mirage!`

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Note:  I'm not an expert in IPA, so if I got the rendering(s) wrong, please correct me.