C182 PLT ACCIDENTALLY TURNED OFF COM WITH S46 WHILE IN THEIR CLASS B AIRSPACE.

Narrative

I WAS RETURNING FROM OLYMPIA; WA; AND WAS APCHING SEA ARPT FROM THE W. CALLED SEA TWR ON 119.9 AND REQUESTED TO TRANSITION THEIR AIRSPACE VIA THE VFR TRANSITION RTE ON MY WAY TO BOEING FIELD. TWR CLRED ME INTO THE CLASS B AIRSPACE AND GAVE ME DIRECTIONS TO OVERFLY THE APCH END OF RWY 34 AT 1500 FT. I MISUNDERSTOOD THIS CLRNC AND PROCEEDED TO OVERFLY THE DEP END OF RWY 34 AT 1500 FT. TO COMPOUND MY ERROR WHILE TRANSITIONING THE CLASS B AIRSPACE; I WAS TUNING IN THE BOEING FIELD ATIS ON THE STANDBY SIDE OF THE RADIO. I INADVERTENTLY HIT THE FREQ SWAP BUTTON ON COM #1 AND PUT TWR'S (SEATTLE'S) FREQ 119.9 ON STANDBY. AFTER 20 SECONDS OF SILENCE; I REALIZED WHAT I HAD DONE AND SWAPPED BACK TO 119.9. AT WHICH TIME SEA TWR STRONGLY INFORMED ME OF MY ERROR IN FOLLOWING THEIR DIRECTIONS AND INFORMED ME TO TURN S AWAY FROM A PIPER NAVAJO (ABOUT 1 MI IN FRONT OF ME) MAKING AN APCH INTO BOEING FIELD. AT THAT TIME THEY INFORMED ME TO CONTACT BOEING TWR AND SVCS WERE TERMINATED. THE ERRORS I MADE WERE NOT CLRLY UNDERSTANDING AND FOLLOWING ATC DIRECTIONS. I SHOULD HAVE QUESTIONED WHY I WAS TO OVERFLY THE DEP END OF RWY 34 WHEN THEY WERE USING RWY 34 AS THE ACTIVE. THE OTHER ERROR WAS WITH CHANGING COM FREQS. IN THE FUTURE I WILL VERIFY THAT I UNDERSTOOD ATC DIRECTIONS EXACTLY AS THEY COMMUNICATED THEM AND WILL ALSO VERIFY WHEN UPDATING COM FREQS THAT I DO NOT CHANGE CURRENTLY USED FREQ. I AM GRATEFUL THAT MY ERROR DID NOT CAUSE A TFC CONFLICT AND BECAUSE OF MY KEEPING WATCH FOR OTHER TFC THERE WAS NOT A CLOSE CALL WITH THE OTHER AIRPLANE.