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1、Optimal Sound Matching Solution through Helmholtz resonator theory 1.Basic theoryHelmholtz Resonator was invented for sound analysis by H.VON Helmholtz(18211894)Its applications are various from bell,violin,guitar and bass speaker cabinet.It features shorter neck and volume bottle than wave as shown
2、 below.Specific frequency depends on air volume in neck(weight)and volume in the bottle(spring)So specific frequency is calculated as below.a a:Necks area()V V :Resonator volume()L L :Necks length(mm)C C :Sound velocity(344m/s)Therefore any shapes of resonator is not affecting Resonant Frequency.If
3、the volume&necks length is same,the resonator has same resonant frequency even in different shape.Basic principleOptimal Sound Matching Solution through Helmholtz resonator theoryEx.1)Whats the resonant frequency in case of a bottle with outer dia.9.8cm,neck length10cm,neck outer dia.3cm?Example Opt
4、imal Sound Matching Solution through Helmholtz resonator theory2.Application (1)Inside structure of handseta :a :Hole total area(m2)SpeakerLCASEV:Front Volumea:Air HoleBack VolumeL :L :Case thickness(m)V :V :Front volume(m3)C :C :344 m/s(RT 20)ApplicationOptimal Sound Matching Solution through Helmh
5、oltz resonator theory(2)Example model:SS1534P-008 -SIZE:15mm X 3.4 H -Fo :850 Hz -Ze :8 ohm(3)Test conditions *Input power:0.1W at 5cmBasic principleOptimal Sound Matching Solution through Helmholtz resonator theoryBKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110
6、dBX:900.00Hz Y:98.92dB ZA:Live Curve TSR fund.SS1534P-008 GRAPH in BAFFLEOriginal test resultOptimal Sound Matching Solution through Helmholtz resonator theory (4)TEST according to some variations Basic Structure Air Hole quantity variation Case thickness variation Front Volume variation Back Volume
7、 variationTest conditionOptimal Sound Matching Solution through Helmholtz resonator theory Basic structure a :1.55mm X 4 ea L:1.55mm V :1.2cc C :344 m/s(RT 20)Back volume:2.42cc=3,486HzBasic structureHand Set Matching Solution with Helmholtz resonatorSpeakerLCASEV:Front Volumea:Air HoleBack VolumeX:
8、3.0000kHz Y:104.23dB ZA:Live Curve TSR fund.BKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110dB3,486Hz 3,000HzTest resultOptimal Sound Matching Solution through Helmholtz resonator theory Air Hole quantity variation a :1.55mm X 4 ea 1.55mm X 2 ea L:1.55mm V :1.2cc
9、 C :344 m/s(RT 20)Back volume:2.42cc=2,465HzAir hole variationOptimal Sound Matching Solution through Helmholtz resonator theorySpeakerLCASEV:Front Volumea:Air HoleBack VolumeBKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110dBX:2.4000kHz Y:101.47dB ZA:Live Curve T
10、SR fund.2,465Hz 2,400HzTest result of air hole changedHand Set Matching Solution with Helmholtz resonator Case thickness variation a :1.55mm X 4 ea L:1.55mm 2.5mm V :1.2cc C :344 m/s(RT 20)Back volume:2.42cc =2,745HzCase thickness changedOptimal Sound Matching Solution through Helmholtz resonator th
11、eorySpeakerLCASEV:Front Volumea:Air HoleBack VolumeBKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110dBX:2.6000kHz Y:102.29dB ZA:Live Curve TSR fund.2,745Hz 2,600HzTest result by case thickness variationOptimal Sound Matching Solution through Helmholtz resonator th
12、eory Front Volume variation a :1.55mm X 4 ea L:1.55mm V :1.2cc 0.8cc C :344 m/s(RT 20)Back volume:2.42cc=4,269HzFront volume variationOptimal Sound Matching Solution through HelmholtzOptimal Sound Matching Solution through Helmholtz resonator theory theorySpeakerLCASEV:Front Volumea:Air HoleBack Vol
13、umeBKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110dBX:3.9000kHz Y:105.25dB ZA:Live Curve TSR fund.4,269Hz 3,900HzTest result by front volume variationOptimal Sound Matching Solution through Helmholtz resonator theory Back Volume variation a :1.55mm X 4 ea L:1.55
14、mm V :1.2cc C :344 m/s(RT 20)Back volume:2.42cc 1.5cc Back volume variationOptimal Sound Matching Solution through Helmholtz resonator theorySpeakerLCASEV:Front Volumea:Air HoleBack VolumeBKMode:TSRA:Frequency Response,Magn dB re 20.00Pa/V1002005001k2k5k10kHz60708090100110dBX:1.3000kHz Y:96.65dB ZA:
15、Live Curve TSR fund.Loss of low soundTest result by back volume changedOptimal Sound Matching Solution through Helmholtz resonator theory3.Conclusion We come to conclusion through proved theory as follows:1)The quantity of front air hole,Resonant Frequency 2)Front case thickness ,Resonant Frequency
16、3)Front volume,Resonant Frequency 4)Back volume,Low sound Optimal acoustic solution in handset design can be coming from Helmholtz resonator theory.qIn case that speaker itself has flat frequency response,specific resonant frequency is generating when being mounted in the handset.Then SPL and sound
17、quality is depending on how the resonant frequency is met with.qIn conclusion the optimal resonant frequency should be set between 2KHz and 5KHz because these area is most sensitive one for human ear.Analysis&ConclusionOptimal Sound Matching Solution through Helmholtz resonator theory HANDSET Design
18、 considerations for Optimal Sound Matching 1.The bigger back volume in speaker,the rich sound at low frequency.2.Sound leakage at front cover is causing decreasing sound at low frequency.3.The bigger sound hole in handset,the clearer sound.4.Should be designed for no interference in between front and back bouncing sound from the speakerHandset design application Optimal Sound Matching Solution through Helmholtz resonator theoryHandset design application Optimal Sound Matching Solution through Helmholtz resonator theory