Buzzer and Speaker 蜂鳴器與喇叭的比較

喇叭與蜂鳴器都是發出聲響的零件,若只是想發出一些警告音,提醒音,這二者其實都是可以使用的:Buzzer and speaker are the acoustic components that can generate sound, if you just need sound to warn or remind, both of them are fine.

蜂鳴器分為電磁式及壓電式二大類,在耗電流,尺寸,頻率,驅動方式上有些不同,但基本上都是將某一個頻點的音壓拉到最高,以期用最小的尺寸,就可以發出很高的音壓,若不在諧振點的音壓就會很小,甚至會相差20dB以上,且蜂鳴器的聲音,由於是用方波發出來的,人耳聽起來就比較刺耳一些,We divide buzzer into piezo and magnetic buzzer. There are some differences in power consumption, dimension, frequency and drive method between piezo and magnetic buzzer, however, both of them basically pull the SPL to the highest at a certain frequent point in order to generate as high SPL as possible in the small size. The SPL will be very low if it is not at the resonance point, even 20dB difference. By the way, the sound of buzzer is drove by square waves; therefore it is harsh to the human ears.

小喇叭是以弦波推動,相較於蜂鳴器人耳聽起來會舒服許多,但因為頻寬較寬,可用的頻率也較低,故在同尺寸時,音壓一定會小於蜂鳴器,且需要音箱的輔助來增進低頻的響應,不然整體的聲音會很小.Micro speaker is drove by the sine waves, to compare with buzzer, the sound is much more comfortable for us. However, the bandwidth is wider, and the frequency is lower, therefore, the micro speaker’s SPL must be lower than the buzzer with the same size, and also need enclosure to help the low frequency, otherwise the sound will be very small.

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.