The advantages of the Microphone Array 麥克風陣列的優點.

With the constant enlargement of the internet bandwidth, the internet video conference has become possible. However, the wide bandwidth does not mean high quality of sound. The consumers usually need to wear the earphones to get the clear sound effects, and it is really inconvenient for them. Therefore, VISTA has already started to support the function of microphone array, which help to record sound more clearly, and can eliminate the noise and wind shear sound in the background. Naturally, besides the support of the operating system, the computer hardware also needs to be matched. Consequently, with the collocation of the microphone array and the DSP, the consumers can easily enjoy using the web phone such as SKYPE without wearing the headsets.
隨著網路頻寬的不斷擴大,使網路上的視訊會議變的可行,
但頻寬夠並不代表聲音的品質就好,消費者常需要佩戴上耳機,才能有清晰的音效,
而這是消費者覺的很麻煩的事,故VISTA已開始支援麥克風陣列的功能,
可使收音的效果更清晰,可消除大部份的背景雜音或風切聲,
當然除了作業系統的支援,硬體上也需配合,故就需要麥克風陣列再加上DSP的搭配,
就可讓消費者再也不用戴耳機,也可以輕鬆的使用SKYPE之類的網路電話功能.

The theory of the microphone array is to set more than two pieces of microphones to record the sound separately, and than the DSP will pick the tonic we want. The simplest design is to pair a unidirectional microphone and an Omni directional one, which can limit the sound receiving range at the width of 120-140 degrees in front of the microphone, and then the SPL will be reduced over 20dB beyond this conical area. This is the reason why the ambient noises can be reduced widely and hardly to be heard.
其原理就是用二顆以上的麥克風,分別收錄聲音,再用DSP加以處理,取出想要的主音源,
最簡單的設計就是以一個單指向的麥克風,,配上另一個全指向的麥克風,
就可以將收音的角度限制在使用的正面約120-140的角度內的圓錐體內,
在此圓錐體之外的音壓會衰減達20dB以上,這就使環境噪音被衰減到幾乎聽不到的程度,
關於設計上的問題,請參考: 麥克風陣列機構設計

The key point of soldering and assembling the microphone 麥克風焊接組裝注意事項

Soldering manufactureThe diaphragm of the microphone is a very thin mylar membrane, it is easily being contracted and distorted with the high temperature. Therefore, we can only use hand-welded method to process, and the temperature of soldering iron cannot over 330°C, the welding work should be done within 2 seconds, the faster the better.The best way is arranging the skilled welders to solder one wire/ pin first, and then finish the left one after the microphone cool down, this can avoid the high temperature causing distortion of the diaphragm, the worse sound receiving results or even breaking down.Otherwise, you can entrust the manufacture to us, our factory has special manufacturing tools to help the microphone cool down. Besides, we will test the sensitivity again after soldering in order to keep the qualification and the reliable quality.
焊接加工
麥克風的振動膜是很薄的塑膠膜,易受高熱影響而收縮變形,
故只能以手焊的方式加工,且烙鐵的溫度不可過高(330度C內),焊接時間需在2秒內,焊接時間愈短愈好,
最好安排請熟綀工焊完一條線(或pin)後,間隔一段時間,待麥克風冷卻後再焊另一條線,
以免過熱使膜片變形,收音效果變差,甚至壞掉.
或可委由我們加工,工廠有專用的製具,可幫助散熱,並會在焊完後再測一次靈敏度是否合格,以確保品質穩定,
Assembling manufacturingThe microphone itself need to aim at the sound hole of the mechanism case, and being as close to the surface of the case as possible in order to gain the best receiving results.Trying to use rubber holder to separate the outside noise, especially the wires type assembling method can do good to fix the microphone on the case of the mechanism.
組裝加工
麥克風本體要對準機殼的音孔,並盡可能的貼近機殼表面,以獲得最好的收音效果,
盡量使用Rubber holder來阻隔外部雜音,尤其是焊線式的組裝方式,也更容易牢靠的裝在機殼上,
When we fabricate the microphone, no matter adding rubber holder or not,
microphone should be pushed to the bottom of the mechanism,
to avoid a chamber forming in front of the sound hole and affecting the sound which microphone receives.
組裝麥克風時,不論有無橡膠套,麥克風都應該要裝到機構的最底部,
以避免形成音腔,而影響麥克風的收音效果.

The interpretation of specification: Watt, Decibel, Hertz, and Resonance

W ( Watt ): A watt = a voltage x an ampere. For example, 330 Watt= 110V x 3 A.
V ( Volt ): V is the unit of voltage, when it needs one joule of work to sent one coulomb of electric from one point to another point, then the potential difference between these two points is one voltage. 
Ohm: Ohm is the unit of impedance in electronics, the higher the impedance is, the less electric current can pass through. 
Hz( Hertz): The frequency of the sound waves vibrate every second. For instance, 100Hz means 100 times vibration in one second. 
dB ( Decibel): dB is the unit of the sound pressure level, which is calculated with logarithm, because the susceptibility to the sound of human ears is not linear. 
Fo ( Resonance Frequency): Fo stands for the resonance point of the speaker. The lower the Fo is, the efficiency of the low frequency is better. 
S.P.L. ( Sound Pressure Level): The volume of the sound. 
Vo-p: The measurement from Vo to the peak, to drive the magnetic buzzer, the waveform is 1/2 square wave. 
Vp-p: The measurement from peak to peak, to drive the piezo buzzer. The waveform is square wave.
W (Watt) :瓦特, 一瓦特= 一伏特的電壓X一安培的電流, 330 Watt= 110V X 3 A.
V (Voltage): 伏特,表示電壓的單位,將一庫侖電荷由一點送到另一點，若須作一焦耳的功，則稱二點間之電位差為一伏特.
ohm : 歐姆,表示電子學上電阻阻抗的單位,阻抗愈高,能通過的電流愈少.
Hz (Hertz): 赫茲,波在每秒振動的次數, 100Hz = 一秒振動100次.
dB (deciBel) : 分貝, 表示音量大小的單位,是以對數算出來的,因為人耳對聲音的敏感度不是線性的.
Fo (Resonance Frequency) : 共振,用來表示喇叭的諧振點,頻率愈低,喇叭低頻的效果會愈好.
S.P.L. (Soudn Presure Level): 音壓位準,即音壓的大小值.
V0-p : 電壓從0V到峰值,用來驅動電磁式蜂鳴器, 波形為1/2方波.
Vp-p: 電壓的峰對峰值,,常用以驅動壓電式蜂鳴器,表示為方波的波形,

The advantages of the Rubber Holder - 使用Rubber Holder的好處

Microphone is a component to receive the sound, therefore it is possible to receive any other sound
which happens near the microphone at the same time, for instant, when we touch the casing;
or the sound made from the fan, the keystroke, and the speaker. However, the rubber holder can
be very helpful to reduce this vibration of sound when the microphone receive the sound, and gives better results.
There are many specifications of holders can meet our microphones without new molding. However,
if you have any special requests for the mechanism, we can also mold for you or offer the useful suggestion on acoustic.
麥克風是用以接受聲音的元件,但它同時也會收到機構內外任何頻率的振動,
如手接觸機殼的磨擦聲,風扇聲,按鍵聲,喇叭聲...等等.
而Rubber Holder可以隔離這些振動,聲音,至少可大幅的衰減之,
使麥克風在收音的時候,可以有更好效果,
我們有許多規格的holder可配合我們的麥克風使用,不需開模,
但若機構上有特殊的要求,我們也可以開模來配合,或是提供聲學上的建議.

Small size speaker but generate higher sound pressure level?

In order to increase sound pressure level, we need to vibrate more air molecule by more power under unit time.
For the two sizes speakers, the area of diaphragms of the 15mm speakers are around 176mm square (7.5*7.5*3.14),
and the 20mm size speakers are around 314mm square(10*10*3.14). The 20mm speakers are only bigger by
5 mm/ 25%, however, the diaphragm are bigger by 78%. Therefore when we input the same power, the 20mm
speakers can vibrate more air at the same time, and it result in higher sound pressure level.
Generally, the speaker in bigger size can provide lower frequency response which is better for human’s
audition. On the other side, we can also provide the smaller speakers more power to make higher sound
pressure level, but it is limited by,
1. Acceptability of the diaphragms2. Thermolysis of the speakers3. After increasing the power, frequency response will change too(because thicker diaphragm, heavier coil..etc)
Therefore, what we can do is reform the material and the structure of the speakers to increase sound pressure level,
but if it is possible to choose the bigger size, the problem of the lower sound pressure level will be improved immediately.
想要有大的音壓,就必需在單位時間之內,以更多的能量來推動更多的空氣分子,
以二種尺寸來說,15mm的喇叭,振膜的面積大約是(7.5*7.5*3.14=176mm平方),
而20mm為(10*10*3.14=314mm平方), 直徑20mm的喇叭雖然在尺寸上只大了5mm / 25%,
但在振膜的表面積卻大了78%,在我們給予這二個喇叭一樣的功率時,
所聽到的聲音大小,就會有很大的不同,就是因為20mm的喇叭可以在同一時間內,
推動更多的空氣分子.
而且更大的尺寸,通常低頻響應也會比較好,人耳所感受的的聲音也會比較好聽些,

當然我們也可以給小喇叭更大的功率,使之發出更高的音壓,但受限於
1. 振膜的承受能力,
2. 喇叭散熱能力,
3. 功率加大後頻率響應特性的改變( 膜片需加厚,音圈變重....)
所以我們只好從材料,喇叭的結構來做改善,盡量將小尺寸的喇叭,聲音做大,
但如果尺寸容許的話,換大一號的喇叭,就可以馬上改善聲音不足的問題囉.