Speak text in a whispered voice.
I want to tell you a secret.
(I am not a real human.)[whisper]
Can you believe it?
n/a
(I am not a real human.)[whisper]
I am not a real human.
<speak>
<amazon:effect name="whispered">I am not a real human.</amazon:effect>.
</speak>
Since Google Assistant doesn’t have a whisper effect, through a configuration setting, you can either ignore the tag:
<speak>
I am not a real human.
</speak>
or use an equivalent:
<speak>
<prosody volume="x-soft" rate="slow">I am not a real human.</prosody>
</speak>