Maha MH-C9000 SUPPORT / FAQ - continuation

[fishinfool]

I've heard the newer ones are quieter than the earlier models. But yes indeed, the C9000 goes beeeep-pause-beeeep-pause... when it's charging.

I bought my 1st last Dec. and the 2nd last Mar. so I guess mine are fairly new. I just now put some cells on to dicharge, then to charge just to see if it does make any kind of noise. I know, I know, get a life right? :laughing:

 

[tandem]

Mine is fairly new. It makes no sound at all. None.

(And for the record I like the nice backlight -- gives me something to navigate to in my office, as I tend to wander the house in the dark at night, even though my EDC light is in my pocket. Perhaps I do this in a vain attempt at trying to prove to myself that I'm not ageing as fast as I really am...)

 

[bcwang]

I can tell you that the newer ones don't make the noise anymore, I've seen 3 samples and all were rid of the whine.

I've had 4 samples of ones from a few years ago and they all had the annoying high pitched whine. I can understand why some couldn't hear it as the frequency is very high. I wouldn't call it a "beep" like some said, for me it is excruciatingly annoying.

In fact, I recently was able to measure the older c9000 and the main whine occurs around 12.83 - 13.74 khz depending on which slot or combinations of slots are used. There were additional spikes at other frequencies higher and lower than that, but this spike was the loudest by quite a few decibels so would stand out the most. Those with loss of hearing in these frequencies would not be able to hear the whine.

 

[Meku]

I can tell you that the newer ones don't make the noise anymore, I've seen 3 samples and all were rid of the whine.

I've had 4 samples of ones from a few years ago and they all had the annoying high pitched whine. I can understand why some couldn't hear it as the frequency is very high. I wouldn't call it a "beep" like some said, for me it is excruciatingly annoying.

In fact, I recently was able to measure the older c9000 and the main whine occurs around 12.83 - 13.74 khz depending on which slot or combinations of slots are used. There were additional spikes at other frequencies higher and lower than that, but this spike was the loudest by quite a few decibels so would stand out the most. Those with loss of hearing in these frequencies would not be able to hear the whine.

Mine is very new (0j0fa) and it still makes the noise. Its very faint but its still there. Its hard to argue about high frequency noise...

 

[csshih]

Mine is very new (0j0fa) and it still makes the noise. Its very faint but its still there. Its hard to argue about high frequency noise...

not if you have test equipment like the quoted poster had!

odd.. I have a 0j0ca, and I cannot detect any high freq. whine. -- and I am very good at detecting them, unfortunately... :sick2:

 

[Meku]

not if you have test equipment like the quoted poster had!

odd.. I have a 0j0ca, and I cannot detect any high freq. whine. -- and I am very good at detecting them, unfortunately... :sick2:

In a way you're right but even then there the subjective differences. Then there are limitations of measurement equipment. Lets say microphone has high frequency response of 15-20 Khz. Most children and some adults can hear all the way to 20 Khz. Some will hear higher then 20 Khz. However, there are much variation in human hearing. Lets put it this way. Most should hear a sound around 12-13 Khz but only few adults will hear a sound of 20 Khz or higher. Therefore, some will think one unit is silent when other one will still hear it.

Regarding high frequency hearing; you either hear it or not. If you don't hear a frequency then you don't hear a sound at all. Its all or nothing here.

 

[Notsure Fire]

Good point. That's a logical way to put it.

 

[Meku]

If you want to test your high frequency hearing you can do it here. However, there is a VERY HIGH possibility that your soundcard won't support anything beyond 20 Khz and some don't go even beyond 15 Khz. There is good possibility that new MH-C9000 has very high frequency charge sound in a range of 17 Khz to 20 Khz so its silent to majority of users.

 

[bcwang]

Mine is very new (0j0fa) and it still makes the noise. Its very faint but its still there. Its hard to argue about high frequency noise...

I tested an 0j0ca with one slot and there is a peak noise at a decently high 46db at 21.76khz. It tapers down to 26db by 20khz. So potentially you could be hearing it, and it would be even worse as this is a much higher frequency. This would explain why most don't hear it though, I think few adults, if any, have hearing above 20khz.

 

[Meku]

I tested an 0j0ca with one slot and there is a peak noise at a decently high 46db at 21.76khz. It tapers down to 26db by 20khz. So potentially you could be hearing it, and it would be even worse as this is a much higher frequency. This would explain why most don't hear it though, I think few adults, if any, have hearing above 20khz.

Sounds like Maha engineered the new units so that vast majority won't be bothered by the noise. 26 dB is not very loud but 46dB at 21.76 kHz could be very annoying indeed. Regarding hearing in general it is commonly stated that humans don't generally hear sounds higher then 20 kHz. Very very small number of adults can hear sounds over 20 kHz. Most adults can't hear a sound over 16 kHz. Normally middle age adults hearing tops at 12-14 kHz. Therefore, for vast majority new MH-C9000 is dead silent. For very few it can be heard and possibly to some "freak of nature" it can be very annoying. To get some perspective, security products like Mosquito which are designed to repel loitering teenagers use sound between 17 kHz to 20 kHz. Any adult hearing them should be happy since that would mean your ears are still in very good condition.

EDIT: Just out of general interest; are you using some high frequency measurement microphone? Must be if you can monitor sounds beyond 20 kHz...

 

[thedeske]

My unit's over a year old and quiet to my ears.
No dog around to test the upper range

 

[pae77]

I never noticed any sound coming from mine (about 2.5 years old). I definitely have diminished ability to hear some high frequencies though. :shakehead

 

[Trancersteve]

The trouble is that my hearing is quite shot to begin with due to loud prolonged headphone usage.

But I am 27.

I thought at around this age the ears start to lose the ability to hear these high frequency noises. But the C9000 sounds terrible and can sometimes be heard from the next room!

I am wondering if I can send it back to Maha even though I have had it for +3 years. Is it worth contacting Maha?

 

[fishinfool]

I am wondering if I can send it back to Maha even though I have had it for +3 years. Is it worth contacting Maha?

I would go ahead and contact them if I were you because who knows, they might surprise you. Plus you have nothing to lose except the time it takes to write the email. I'm very interested to see what they say. Keep us posted.

 

[csshih]

haha, OW!
guess my high freq hearing sucks.. I can only start hearing @ 17kHz..

 

[bcwang]

EDIT: Just out of general interest; are you using some high frequency measurement microphone? Must be if you can monitor sounds beyond 20 kHz...

Surprisingly, it is an iphone app my friend has on his iphone 4. And if you have the 3gs or newer it is supposed to measure quite flat and samples at 48khz so up to 24khz sound can be detected. It's pretty awesome what you can do with an iphone these days.

http://www.faberacoustical.com/products/iphone/signalscope/

 

[Meku]

haha, OW!
guess my high freq hearing sucks.. I can only start hearing @ 17kHz..

Not necessarily. If you're in your teens then you can expect to hear frequences higher then 16kHz. Even then there is good chance you won't be hearing sounds as high as 20kHz. If you're an adult then hearing a 17kHz or higher is an excellent result. In reality high frequency hearing starts to go down at very early age. In general humans have best high frequency hearing at age of 8. For some reason males suffer more high frequency hear loss then females.

Also there is a possibility that when testing high frequency hearing your system might start anti-aliasing the sound so there is chance that no sound comes out of your system at very high frequencies.

 

[Meku]

Surprisingly, it is an iphone app my friend has on his iphone 4. And if you have the 3gs or newer it is supposed to measure quite flat and samples at 48khz so up to 24khz sound can be detected. It's pretty awesome what you can do with an iphone these days.

With iPhone and such there is a "problem" of high frequency anti-aliasing. Set ups like these start to anti-aliase sound somewhere between 20 kHz and 24 kHz. Also you need to have high frequency measurement microphone to monitor high frequencies reliably. High frequency measurement microphones go to very high frequencies such as 150 kHz. Normal recording microphones top out at 20 kHz. After that they are not reliable. Since you managed to record 46db at 21.76khz it would suggest that there is a good chance 0j0ca MH-C9000 makes lot of noise at very high frequencies.

 

[Turbo DV8]

I have 2 c9000's and I haven't noticed any noise coming from them but the 'always on' bright led display bothers me at night though. So I guess that means that my hearing is shot.

You need to look on the bright side of that. At least you know you're not blind!

 

[fishinfool]

You need to look on the bright side of that. At least you know you're not blind!

That's funny Turbo!