Car Audio Modification: From Beginner to Expert
Do you feel the original sound lacks layering, has a narrow soundstage, or thin vocals?
Even after an upgrade, are highs not bright enough or lows not powerful?
Do you find listening to the radio better than music on the original system?
If you answered yes to any, you might need to upgrade your car audio. If unsure how, follow us! Every Mon, Wed, Fri, Very City Auto brings a special course – Car Audio Modification: From Beginner to Expert. Spend just minutes reading each lesson; learn easily!
I. Acoustics Knowledge in Three Parts
(A) Sound
Sound is the vibration of air molecules. Vibration of an object ("sound source") causes corresponding air molecule vibration, transmitted to the eardrum, processed by auditory organs, allowing us to hear. Not all air molecule vibrations form sound; vibrations follow patterns described as "waves". Let's briefly explain "sound waves":
(B) Sound Waves
Throwing a stone into calm water creates outward-spreading ripples – a visible "wave". Sound waves from vibrating air molecules are more complex: they spread spherically from the source as compression waves. Air molecules don't travel from source to ear; they vibrate locally, causing adjacent molecules to vibrate, transmitting sound quickly (331 m/s in air).
Example: Sound waves resemble wheat field waves. Particle vibration direction parallels wave motion direction. Waves need a medium; wheat waves stop at ridges; sound waves use air molecules. Thus, sound cannot travel in a vacuum.
(C) Sound Frequency
Vibrations per second = Frequency.
20Hz~20KHz = Audible Sound;
>20KHz = Ultrasound;
<20Hz = Infrasound.
Humans cannot hear ultrasound/infrasound. Bats "hear" ultrasound. Earthquakes/tsunamis emit infrasound.
Rarely does pure single-frequency sound exist; most sounds are complex. Instrument notes are periodic complex sounds; speech is non-periodic.
Conceptualizing frequency:
● Bass drum "booms": Low frequency (~tens of Hz)
● Human voice: Mainly 200Hz-4000Hz
● Gongs/Bells: ~2000Hz-3000Hz
In speech: Female > Male pitch; Child > Adult pitch; "Ah" lower, "Ee" higher, "Sh/Ch" highest. Useful for testing hearing aid frequency response.
II. Fundamental Sound Properties
(A) Sound Wave Propagation Characteristics
Sound waves exhibit reflection, refraction, diffraction, and interference during propagation:
(1) Reflection & Refraction: When sound waves hit an interface between different media, reflection occurs. Hitting an obstacle, part refracts into it.
(2) Diffraction: Sound waves bend around obstacle edges, continuing propagation.
(3) Interference: Sound waves of identical frequency superimpose, strengthening sound in some areas, weakening in others.
Beyond these, absorption/transmission, resonance, and attenuation occur.
(B) Three Elements of Sound
Sound characteristics are mainly expressed through Volume, Pitch, and Timbre.
(a) Volume (Loudness): Subjective perception of sound intensity. Primarily depends on sound wave amplitude.
(b) Pitch: Subjective perception of sound highness/lowness. Primarily depends on frequency.
(c) Timbre: Subjective perception of sound character. Primarily depends on spectral structure.
The Three Elements of Sound
Audible Sound Intensity & Frequency Range
III. Basic Human Auditory Characteristics
(A) Audible Range
Audible Sound, Hearing Threshold, and Pain Threshold define the auditory range.
(1) Audible Sound: Sounds a normal person can hear, frequency range 20 Hz ~ 20 kHz (Audio Frequency).
(2) Hearing Threshold: Audible sound requires minimum intensity. The lowest sound pressure level (SPL) audible is the Hearing Threshold, frequency-dependent. In good conditions, young adults with normal hearing have thresholds near 0 dB (corresponding to 0.00012 Pa) between 800~5000 Hz.
(3) Pain Threshold: SPL causing ear pain. Less frequency-dependent. Typically, 120 dB causes discomfort; >140 dB causes pain; >150 dB risks acute damage.
(B) Equal-Loudness Contours
Equal-Loudness Contours reflect the basic characteristic of loudness perception for pure tones at different frequencies.
(1) Human ears are most sensitive to loudness in the 3~4 kHz range. Sensitivity decreases for lower and higher frequencies.
(2) Higher SPLs yield flatter equal-loudness curves. Different SPLs show large curve differences, especially at low frequencies. Thus, loudness compensation (e.g., Loudness control) is needed during playback, especially at low volumes.
Even after an upgrade, are highs not bright enough or lows not powerful?
Do you find listening to the radio better than music on the original system?
If you answered yes to any, you might need to upgrade your car audio. If unsure how, follow us! Every Mon, Wed, Fri, Very City Auto brings a special course – Car Audio Modification: From Beginner to Expert. Spend just minutes reading each lesson; learn easily!
I. Acoustics Knowledge in Three Parts
(A) Sound
Sound is the vibration of air molecules. Vibration of an object ("sound source") causes corresponding air molecule vibration, transmitted to the eardrum, processed by auditory organs, allowing us to hear. Not all air molecule vibrations form sound; vibrations follow patterns described as "waves". Let's briefly explain "sound waves":
(B) Sound Waves
Throwing a stone into calm water creates outward-spreading ripples – a visible "wave". Sound waves from vibrating air molecules are more complex: they spread spherically from the source as compression waves. Air molecules don't travel from source to ear; they vibrate locally, causing adjacent molecules to vibrate, transmitting sound quickly (331 m/s in air).
Example: Sound waves resemble wheat field waves. Particle vibration direction parallels wave motion direction. Waves need a medium; wheat waves stop at ridges; sound waves use air molecules. Thus, sound cannot travel in a vacuum.
(C) Sound Frequency
Vibrations per second = Frequency.
20Hz~20KHz = Audible Sound;
>20KHz = Ultrasound;
<20Hz = Infrasound.
Humans cannot hear ultrasound/infrasound. Bats "hear" ultrasound. Earthquakes/tsunamis emit infrasound.
Rarely does pure single-frequency sound exist; most sounds are complex. Instrument notes are periodic complex sounds; speech is non-periodic.
Conceptualizing frequency:
● Bass drum "booms": Low frequency (~tens of Hz)
● Human voice: Mainly 200Hz-4000Hz
● Gongs/Bells: ~2000Hz-3000Hz
In speech: Female > Male pitch; Child > Adult pitch; "Ah" lower, "Ee" higher, "Sh/Ch" highest. Useful for testing hearing aid frequency response.
II. Fundamental Sound Properties
(A) Sound Wave Propagation Characteristics
Sound waves exhibit reflection, refraction, diffraction, and interference during propagation:
(1) Reflection & Refraction: When sound waves hit an interface between different media, reflection occurs. Hitting an obstacle, part refracts into it.
(2) Diffraction: Sound waves bend around obstacle edges, continuing propagation.
(3) Interference: Sound waves of identical frequency superimpose, strengthening sound in some areas, weakening in others.
Beyond these, absorption/transmission, resonance, and attenuation occur.
(B) Three Elements of Sound
Sound characteristics are mainly expressed through Volume, Pitch, and Timbre.
(a) Volume (Loudness): Subjective perception of sound intensity. Primarily depends on sound wave amplitude.
(b) Pitch: Subjective perception of sound highness/lowness. Primarily depends on frequency.
(c) Timbre: Subjective perception of sound character. Primarily depends on spectral structure.
The Three Elements of Sound
Audible Sound Intensity & Frequency Range
III. Basic Human Auditory Characteristics
(A) Audible Range
Audible Sound, Hearing Threshold, and Pain Threshold define the auditory range.
(1) Audible Sound: Sounds a normal person can hear, frequency range 20 Hz ~ 20 kHz (Audio Frequency).
(2) Hearing Threshold: Audible sound requires minimum intensity. The lowest sound pressure level (SPL) audible is the Hearing Threshold, frequency-dependent. In good conditions, young adults with normal hearing have thresholds near 0 dB (corresponding to 0.00012 Pa) between 800~5000 Hz.
(3) Pain Threshold: SPL causing ear pain. Less frequency-dependent. Typically, 120 dB causes discomfort; >140 dB causes pain; >150 dB risks acute damage.
(B) Equal-Loudness Contours
Equal-Loudness Contours reflect the basic characteristic of loudness perception for pure tones at different frequencies.
(1) Human ears are most sensitive to loudness in the 3~4 kHz range. Sensitivity decreases for lower and higher frequencies.
(2) Higher SPLs yield flatter equal-loudness curves. Different SPLs show large curve differences, especially at low frequencies. Thus, loudness compensation (e.g., Loudness control) is needed during playback, especially at low volumes.