Hey there MARKD8012,
It sounds like you can hear from the speakerphone just fine but the person you are talking to says you sound faint. You were on the right track in looking for information about troubleshooting the speaker, but I would next use this article to help troubelshoot microphone issues:
iPhone: Microphone issues
http://support.apple.com/kb/ts5183

- Make sure nothing is plugged in to the jack connector.
- Make sure nothing is blocking any of the microphones (refer to the pictures below to find your device's microphones). Check for these:
- Dirt or debris
- A screen protector or case
- When you're holding your phone next to your ear, make sure you don't block the microphone with your fingers or shoulder and make sure to speak into the microphone
- Turn the iPhone off and then on.
- Update to the latest version of iOS.
- If necessary, find general iPhone hardware troubleshooting suggestions.
- For further assistance, contact Apple Support.
Thank you for using Apple Support Communities.
All the best,
Sterling