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This is not a scientific study but may be useful for comparison purposes if enough people participate. It would be important for those without wind noise to participate too.
Download the iPhone app Decibel 10th by Skypaw(free). Measure the decibel level at 70 MPH with the phone held near the top of the steering wheel and post results here. Please note if you have wind noise or not. Also, note your device. I am using an iPhone 6. Different devices may have different microphone sensitivity.
Lots of variables in this test, but why not?
This is a link to a chart of noise levels in various cars at different speeds. It might be useful as a comparison to the results of this thread. The 2014 C300 is listed. The W205 is not.
I tried it with the Skypaw Decibel 10th App on an iPhone 6.
C400
19 inch wheels
Pirelli Sottozero run flat tires
DISTRONIC set to 70mph
Average condition highway
I don't have the excessive wind noise described in these forums
I found the App to be overly sensitive. The reading bounces around quite a bit making it difficult to get a stable reading, so I don't know how valuable this will be. At its quietest, with no traffic nearby, my reading varied between 70-74 db at 70 mph. Sound dropped below 70 db between 60 and 65 mph. Passing traffic raised the noise level to the upper 70s db. Changes in pavement also caused significant swings in sound level.
I tried the app and saw the same variation. Lowest near 68 at 60mph, but road surfaced chaned a lot as did position of phone. If held near driver glass in 20mph wind at 70 and it was around 82db. I should be wearing hearing protection at that level based on osha.
So far I was only able to test it on a two lane road, going 55 mph. I agree that the decibel figure bounced around so much it was hard to pick a number. But holding it above the steering wheel I got around 74, and near the drivers side window around 77...there may have been cars passing from the other direction that I didn't notice because I was concentrating looking at my iPhone and listening to my wife squawk asking what the heck I was doing. I'll try it alone next time.
I didn't notice because I was concentrating looking at my iPhone and listening to my wife squawk asking what the heck I was doing. I'll try it alone next time.
That's so funny. The exact same thing happened to me. I tried it this morning with my wife in the car. Her questions and complaints made the readings more variable and much higher. I had to take a solo ride later in the afternoon to get good readings.
I use the iPhone app called "audio tool" or "Decibel Meter Pro" by performance audio for my home theater tuning. It works great but costs .99 cents. It has adjustable sensitivity and a peak value hold.
The pro audio tool version is really nice. I don't remember how much it was, maybe 3.00 but it can do a lot more. Tone generator to find rattles, microphone, audio scope, tempo, ect....
I don't have my car yet. Due in another couple weeks. Supposedly being built next week. I will post results once I get it.
Here's my reading from today on the commute home
Using decibel 10th
Average 83db!
Conti 18 in run flats, highway good condition
110kmh (@70mph)
No squawking spouses
From my experiment, I don't believe the phones microphone and this app are worth much. The microphone is designed to be sensitive to pick up sound in the voice range and cut high/low sounds, not the a more full spectrum.
Another problem with random measurements is the inconsistency of the ambient sound environment. How do you differentiate between tire noise, road noise, traffic noise, and wind noise? You can't.
I've been over roads that were whisper quiet, and also over surfaces that sounded like the inside of a washing machine. My car has almost no wind noise, but heavy cross winds will be heard. My snow tires give off a steady hum, my standard Conti's do not. This may be an interesting exercise, but I can't see how it will help define the wind noise problem since the testing varies so much.
Here's my reading from today on asphalt; road in good condition.
Using decibel 10th
Average ~80-85db!
Conti 18 in run flats, sports suspension
70mph
I agree, this app is too sensitive.
I tried this again using the Decibel Meter Pro (a much better app...more stable in the readings). Driving 62 mph, on a nice smooth asphalt road I got 58 decibels at the top of the steering wheel and 60 decibels near the top of the drivers window. No wind today.
I tried it with the Skypaw Decibel 10th App on an iPhone 6.
C400
19 inch wheels
Pirelli Sottozero run flat tires
DISTRONIC set to 70mph
Average condition highway
I don't have the excessive wind noise described in these forums
I found the App to be overly sensitive. The reading bounces around quite a bit making it difficult to get a stable reading, so I don't know how valuable this will be. At its quietest, with no traffic nearby, my reading varied between 70-74 db at 70 mph. Sound dropped below 70 db between 60 and 65 mph. Passing traffic raised the noise level to the upper 70s db. Changes in pavement also caused significant swings in sound level.
I tried it again today with a different app, Decibel Ultra. I traveled the same route at the same speed. The readings were much more stable and consistent with the data in the link in post 2 above.
I got consistent readings of 62-63 in the center of the car above the touchpad controller at ear level. 63-65 at ear level near the drivers window. Very little difference.
Who knows how accurate these apps are or what the results actually mean, but these results are consistent to what I hear, a very quiet ride.
Check your app settings for 'Weighting'. There are usually four weighting filters (A, B and C and Linear) that will drastically alter the overall dB level the meter (or app) shows. Ideally A-weighting should be used for this type of measurement and will yield results in the mid 60s to low 70s (for 70mph cruise) depending on environmental conditions. Levels in the 80s are probably on a 'Linear' setting and would not be comparable to settings a different weighting scheme. A-weighted is widely used in human factors as it is designed to mimic the way the human ear "hears" as we don't hear all frequencies the at the same level as a microphone does (or is supposed to).
If there is no way to tell what weighting scheme the app is using then comparing results will be harder.
Check your app settings for 'Weighting'. There are usually four weighting filters (A, B and C and Linear) that will drastically alter the overall dB level the meter (or app) shows. Ideally A-weighting should be used for this type of measurement and will yield results in the mid 60s to low 70s (for 70mph cruise) depending on environmental conditions. Levels in the 80s are probably on a 'Linear' setting and would not be comparable to settings a different weighting scheme. A-weighted is widely used in human factors as it is designed to mimic the way the human ear "hears" as we don't hear all frequencies the at the same level as a microphone does (or is supposed to).
If there is no way to tell what weighting scheme the app is using then comparing results will be harder.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Originally Posted by StanNH
Another problem with random measurements is the inconsistency of the ambient sound environment. How do you differentiate between tire noise, road noise, traffic noise, and wind noise? You can't.
I've been over roads that were whisper quiet, and also over surfaces that sounded like the inside of a washing machine. My car has almost no wind noise, but heavy cross winds will be heard. My snow tires give off a steady hum, my standard Conti's do not. This may be an interesting exercise, but I can't see how it will help define the wind noise problem since the testing varies so much.
+1^ & how are you going to calibrate devices to be meaningful. A Radioshack meter can vary by over 5 db between 2 apparently identical units ~ I've seen them out by over 10db. Whether A or C etc. weighting is used ad nauseum. Then there is frequency range to consider & how flat the response is.
You will end up comparing apples with pears.
Last edited by Glyn M Ruck; 03-30-2015 at 07:50 PM.
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Here is the typical (in the broadest sense) Radioshack SPL meter response curve. I hate to think what an iPhone would look like. They use crap uncalibrated microphones to cover voice frequency range only.
03-28-2015, 10:47 AM
