Earitating Noise Levels
 

Attention 05+ Legacy Owners

I own a 2006 legacy wagon but find on the highway no matter how much I fiddled with the sound system I can never get it to sound good without my wife complaining it was to load and I would have to agree. We began to pay more attention and found that we were always adjusting the volume as we went to work – suburbs – highway – city streets. Funny thing is we do not adjust the volume in our 99 Subaru wagon and can still hear the radio at highway speeds though it is a bit diminished.

The science part: I have a sound pressure meter so measured the radio volume we use in the 99 and using the meter adjusted the volume of the ‘06 radio to the same level. On our next drive to work we found at highway speeds we could barely hear the radio.

On the next trip to work I brought the sound pressure level meter and found that at 70 MPH my new car had a sound pressure level or ~70dba at head level between the heads of the front seat passengers. This is better than my 99 as it is ~74dba but dba or db a-weighted only samples the frequency range of human voice. I did another measurement using dbc or c-weighted (closer to the range of human hearing) and found the sound pressure level to be greater than 90 dbc and as high as 95bdc. The old 99 wagon is between 84 and 88db, which is a big difference in sound level.

My guess is the car is creating low frequency noise that is hard to identify but is drowning out the radio.

I returned my car to the dealer and they are not sure what to make of this. They claim no one has ever complained, so I have to ask.

Have others noticed the need to raise the radio volume level with speed. Maybe you experience a numbing feeling in you ear somewhat like when you are in an airplane. Maybe you find there is a need for more bass or the treble needs set below 0.

An interesting observation with scientific measurements.

I used to own an econobox, and the road noise would kill me on highway drives. I ended up soundproofing the POS, which helped considerably.

I'm not talking about a "dynamat 'till you drop" approach. For reducing road noise, an acoustic barrier material under the floor carpet (tranny tunnel as well) is your best bet. I used Cascade Audio VB3 and VB4. The VB3 has a 1/64 inch lead foil layer sandwiched between closed cell foam layers. It's 1/4 inch thick and weighs 1 lb/sqft.

Soundproofing worked so well on my old POS that I did it to my 2003 Legacy Wagon. The reduction in noise wasn't as dramatic, but it did noticeably quiet things down. It especially helped the bass frequencies. All told, I added about 50 lbs of barrier and damping materials to achieve what 100-150 lbs of dynamat alone would do.

Other points to consider:

Your 2006 wagon has wider, lower profile tires than the '99. This will noticeably increase road noise. Choosing quiet tires (check Tirerack) can help with this problem. You can also switch to a taller profile tire on a smaller wheel. You basically trade better handling for lower tire noise.

If the 2006 rides slightly lower to the ground than the '99, this will also increase road noise. Was the '99 an Outback?

If you don't want to rip up your carpeting (it's not difficult, just time consuming), you can try a spray undercoating like Wurth SKS. This is a water-based (non-asphalt) rubberized substance. The bonus here is that a properly prepped and applied undercoating can help with rust issues by minimizing rock chips on metal surfaces.