Must a creature be able to hear the caster’s whisper to be targeted by the Dissonant Whispers spell?

Dissonant whispers says:

You whisper a discordant melody that only one creature of your choice within range can hear, wracking it with terrible pain. The target must make a Wisdom saving throw.

I initially took the first sentence to mean that the creature must be able to hear the caster’s whisper to be targeted by dissonant whispers, but now I’m not so sure.

Perhaps I’ve read it one too many times… although only one creature can hear the whisper, the spell doesn’t require that the creature must hear the whisper. Am I reading too much into this?

Audio and video solution with “whisper” support that is not roll20

For our online gaming sessions we use Fantasy Grounds as our virtual table top. We’ve also tried a number of other solutions that work o a certain extent but without fully support all our needs which are as follow:

  1. Voice and video.
  2. Ability to stream my own music from iTunes
  3. Ability to speak (whisper) only to one of the players.
  4. Good audio quality.

So far, we’ve tried:

  1. Discord + Voicemeeter: no whisper, bad music quality. Excellent video and voice.
  2. Ts + Voicemeeter. No whisper, no video. Excellent music and voice quality.
  3. Roll20. Bad experience, only preuploaded music. Normal video and audio and whisper support.
  4. Roll20 + Ts + Voicemeeter. Complicated setup, normal audio and video quality. Meets all requirements.

So far option 4 works but it is far from ideal and I was wondering if there was a better solution.

Does Shadow Lore require the Bard to physically whisper, and could the target or a nearby creature detect this?

A 14th level College of Whispers Bard gains the following class feature:

Shadow Lore: As an action, you magically whisper a phrase that only one creature of your choice within 30 feet of you can hear. The target must make a Wisdom saving throw against your spell save DC. It automatically succeeds if it doesn’t share a language with you or if it can’t hear you. On a successful saving throw, your whisper sounds like unintelligible mumbling and has no effect.

If the target fails its saving throw, it is charmed by you for the next 8 hours or until you or your allies attack or damage it. It interprets the whispers as a description of its most mortifying secret.

While you gain no knowledge of this secret, the target is convinced you know it. While charmed in this way, the creature obeys your commands for fear that you will reveal its secret. It won’t risk its life for you or fight for you, unless it was already inclined to do so. It grants you favors and gifts it would offer to a close friend.

When the effect ends, the creature has no understanding of why it held you in such fear.

(pg 16, Xanathar’s Guide to Everything)

When using Shadow Lore, would the Bard physically whisper something that only the Target can hear, or is it more like a telepathic whisper that the target hears?

Would the target, or a nearby creature, be able to tell that Shadow Lore was used and potentially who used it?