I listen to music, audiobooks and lectures when I walk. Headphones and earphones block the environmental noise to the extent I often do not hear approaching cars, which is a safety issue on country roads. If I use Bluetooth enabled HAs, how much microphone is combined with the audio stream? For an example, older telephone handsets provided a certain amount of feed from the mouthpiece to the earpiece, else people tended to shout into the phone. Do the HAs feed some microphone into the audio stream?