What sound do non-native speakers tend to produce when they mispronounce /f/ and/or /v/ in English? [closed]

If you look at the way the ancient Greeks spelled Hebrew names from the Bible, it looks like they would have pronounced /f/ as /pʰ/ and /v/ as /b/. Since English doesn't distinguish between /pʰ/ and /p/, the easiest thing would be for you to have the harpies use /p/ for /f/ and /b/ for /v/.

Which sounds you make when you mispronounce a phoneme that isn't in your language depends very much on your native language. For example, the sound of "th" in the, /ð/, tends to be pronounced as /z/ by French speakers, but is quite likely to be pronounced /d/ by German speakers.

You can guess how the Greeks would have pronounced /f/ and /v/ by the way they transcribed biblical names.

Hebrew has both a /f/ and a /p/ sound, and they are transcribed by the Hebrew letter pay (פ) . Today, you add a dot (called a dagesh) to distinguish these pronunciations, but this innovation was added to Hebrew after the Bible was written. The Greeks transliterated the /p/ sound of pay as pi (Π) and the /f/ sound as phi (Φ). For example, the name Potiphar has two pays, and the first one turned into pi and the second into phi.

Similarly, the Hebrew letter bet (ב) can represent both /b/ and /v/. The Greeks transcribed both sounds as a beta (Β); for example Abraham is pronounced with a /v/ in Hebrew, but the Greeks transcribed it with a beta, which is why we pronounce it with a /b/.