No sound emitting from your iPod Touch's internal speakers probably means you'll need to do some hardware troubleshooting. Sometimes it can indicate a software problem as well. In most cases you'll just need to adjust one of the iTouch's small settings, like those for volume or Bluetooth. Only after you've tried all of the basic troubleshooting should you call Apple to see if you need the speakers replaced.
Turn the volume up. Some songs and games have their volume settings low, so your volume must be up higher to hear them. Try playing a different song to test it.
Turn off Bluetooth on your iPod Touch to make sure the sound and volume are not being diverted to Bluetooth headphones.
Try disconnecting any headphones you have plugged in, and then try both plugging in and unplugging a pair of headphones. Sometimes in older iPod Touches the headphone port needs to be toggled more than once in order to activate the speakers.
Restart and Restore
Turn the iPod Touch off, and then on again. If none of these steps work, plug the iPod into your computer, open iTunes, and click "Restore." This will re-install the operating system on your iPod Touch and can fix any software problems that might be interfering with the speakers. Doing this does wipe all content from your iPod Touch, so after you restore, you'll need to re-sync your music, apps, videos, contacts, and any other data.