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Here are some interesting numbers, collected from a variety of sources, that help one to understand the volume levels of various sources and how they can affect our hearing.

NOTES:

• One-third of the total power of a 75-piece orchestra comes from the bass drum.
• High frequency sounds of 2-4,000 Hz are the most damaging. The uppermost octave of the piccolo is 2,048-4,096 Hz.
• Aging causes gradual hearing loss, mostly in the high frequencies.
• Speech reception is not seriously impaired until there is about 30 dB loss; by that time severe damage may have occurred.
• Hypertension and various psychological difficulties can be related to noise exposure.
• The incidence of hearing loss in classical musicians has been estimated at 4-43%, in rock musicians 13-30%.

Statistics for the Decibel (Loudness) Comparison Chart were taken from a study by Marshall Chasin , M.Sc., Aud(C), FAAA, Centre for Human Performance & Health, Ontario, Canada. There were some conflicting readings and, in many cases, authors did not specify at what distance the readings were taken or what the musician was actually playing. In general, when there were several readings, the higher one was chosen.

• A decibel (named for Alexander Graham Bell) is a tenth of a bel, and is used as an expression of power. Here's where the confusion arises: A decibel isn't a measure of ANYTHING; it is a ratio of two power levels. Because of the way our ears perceive volume, these ratios follow a logarithmic curve, expressing them as a decibel keeps things easier to deal with. Here are a few convenient decibel figures worth remembering: One decibel is commonly taken as the smallest volume change the human ear can reasonably detect. Doubling the POWER of an amplifier results in a 3 dB increase, which is a "noticeable" volume increase. Doubling the VOLUME of a sound is a 6 dB increase (you may occasionally see 10 dB listed as the "double-volume" figure, 6 dB is the more mathematically correct number). By doing the math, you can see that truly doubling your volume actually requires 4 times the amplifier power! Keep these figures in mind the next time you are comparing the specs of two pieces of equipment...
  
  Decibels are used all over the place in audio measurements and specifications partly because it is very easy to express extremely large or small values with decibels due to their logarithmic nature. The full depth of the topic is well beyond the scope of this writing, but suffice to say that the decibel always refers to a ratio of two values. It is never an absolute value. Thus when we speak of losses and gains in audio we use dB to quantify those values. If a signal goes into a unit and is output at a lower level it is said to be down by some value of dB. Decibels come in many variants: dB PWL, dB SPL (also known as Sound Pressure Level), dBm, dBu, dBV, dBv, and more.

Logitech was went webcam wacko today by unveiling four such peripherals which are aimed towards bringing 720p video calling to as many PC users as possible - the D Pro Webcam C910 ($99.99), HD Webcam C510 ($59.99), HD Webcam C310 ($49.99) and HD Webcam C270 ($39.99).

Logitech's upcoming webcams feature USB connectivity, enable 1-click Facebook and YouTube HD upload, include universal clips to fit a wide range of hardware, and make use of the new Vid HD software.

“HD video calling is a critical step toward our vision of a world in which video communication is as mainstream and seamless as a telephone call - for anyone, anywhere,” said Eric Kintz, vice president and general manager of Logitech's video business. “With Logitech HD webcams and Vid HD, you have everything you need to share, to connect, to see the people that matter to you in breathtaking detail that far surpasses the quality of embedded webcams.”

The HD Webcam C510, C310 and C270 are set to make their debut this month, in the US, while the HD Pro Webcam C910 will arrive in August. For more info about Logitech's webcams see this page .

HD Pro Webcam C910

HD Webcam C510

HD Webcam C310

• Digital Cinema 4K
  (4096 x 2160)  : 36.5MB
• UHDTV
  (7086 x 4320) : 94.9MB
• RED EPIC
  (280,000 x 9,334) : 500MB
  

  The Red Epic is announced to come in the following variants:

  Name	Physical Size	Resolution (in pixels)	Estimated Price
  Epic-X S35	30mm x 15mm	5,120 x 2,700(5K)	$10,500 (+) RED1 body
  Epic S35	30mm x 15mm	5,120 x 2,700	$28,000
  Epic FF35	36mm x 24mm	6000 x 4000(6K)	$33,000
  Epic 645	56mm x 42mm	9,334 x 7,000(9K)	$43,000
  Epic 617	168mm x 56mm	28,000 x 9,334(28K)	$53,000

  
  

아이폰은 스마트폰 전용 요금제가 아니면 가입이 되지 않습니다. 즉, 무료통화와 무료문자.. 그리고 무료 데이터 용량이 기본적으로 제공됩니다. 어제 쓰지 않고 남은 데이터 용량의 경우 다음달로 이월해서 쓰도록 해준다는 발표가 있었는데.. 무료 문자는 해당 사항이 없습니다. 즉, 사용하지 않으면 그냥 소멸되는 것이니 좀 아깝습니다.

일반 요금제에서는 SMS와 MMS 요금에 큰 차이(사진을 보내는 MMS와 동영상을 전송하는 MMS 요금도 다릅니다)가 있지만.. 아이폰에서 제공하는 무료문자는 동일하다고 합니다. 즉, 문자메시지를 보내던지, 사진 MMS를 보내던지.. 또는 동영상 MMS를 보내던, 무료문자에서 1건이 차감된다는 이야기입니다.

자신의 요금제 범위 내에서 문자가 모자라는 분도 더러 있겠지만.. 대부분 문자가 남을텐데요.. 아이폰의 강력한 메시징 기능을 활용해서 MMS를 많이 소진해 보시죠.

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