# Bluetooth Hearing Aid EQ Mixer UI for iOS > By Lawrence Arya, Founder & CEO of VP0. Published 2026-06-18. 7 min read. > Source: https://vp0.com/blogs/bluetooth-hearing-aid-eq-mixer-ui-ios How to build a hearing aid EQ mixer on iOS, from the SwiftUI band sliders to the AVAudioEngine path, with the limits on what an app can actually equalize. **TL;DR.** A hearing aid EQ mixer screen lets a user shape the sound of Bluetooth hearing devices: per-band gain sliders, presets for noisy or quiet places, and a balance control. On iOS the UI is straightforward SwiftUI, vertical sliders bound to band gains, but the audio path is the real constraint: app-controlled equalization works on audio your app plays through AVAudioEngine and AVAudioUnitEQ, while system-wide tuning of Made for iPhone hearing devices runs through Apple's accessibility frameworks. Build against the audio you control, label bands in Hz, and treat it as comfort tuning, not a medical fitting. The screen is fastest to start from a free VP0 design with Claude Code or Cursor. A hearing aid EQ mixer screen lets someone shape the sound of their Bluetooth hearing devices: per-band gain sliders, presets for noisy or quiet rooms, and a left-right balance control. On iOS the interface is straightforward SwiftUI, vertical sliders bound to band gains with clear labels, but the audio path is the real constraint. App-controlled equalization works on audio your own app plays, through `AVAudioEngine` and `AVAudioUnitEQ`, while adjusting Made for iPhone hearing devices system-wide runs through Apple's accessibility frameworks rather than open app access. Build the mixer against the audio you actually control, label every band in hertz and decibels, and treat it as comfort tuning rather than a medical fitting. The screen is fastest to start from a free [VP0](/explore) design with Claude Code or Cursor. ## What an EQ mixer screen needs to show It has to make frequency shaping legible at a glance, then let the user go deeper. The core is a row of vertical sliders, one per frequency band, each labeled with its center frequency and current gain in decibels. Around that sit presets for common situations, restaurant, outdoors, music, speech, a master balance for left and right, and ideally a simple output meter so the user sees the effect register, the kind the [audio waveform recorder UI](/blogs/audio-waveform-recorder-ui-react-native/) uses. The audience shapes the design. People reaching for a hearing EQ often want larger touch targets, high contrast, and labels they can actually read, so generous sliders and explicit numbers beat a dense graphic curve. Apple's [accessibility guidance](https://developer.apple.com/accessibility/) is the right lens here: clarity and legibility first. ## The audio path is the real constraint What you can equalize depends on where the audio comes from. Your app can apply a real EQ to audio it plays itself by inserting an [AVAudioUnitEQ](https://developer.apple.com/documentation/avfaudio/avaudiouniteq) node into an [AVAudioEngine](https://developer.apple.com/documentation/avfaudio/avaudioengine) graph, which is the clean, supported path for a media or hearing-assist app you build. System-wide tuning of certified Made for iPhone hearing devices is handled by iOS accessibility features, not by giving any app raw control of another app's or the system's output. | Where EQ applies | API to use | What you control | | --- | --- | --- | | Audio your app plays | AVAudioUnitEQ in AVAudioEngine | Full per-band gain | | MFi hearing devices, system | Apple accessibility features | User settings, not raw DSP | | Generic Bluetooth output | AVAudioSession routing | Route and volume, not arbitrary EQ | Design for the column you are actually in. A hearing-assist app that captures and replays sound owns its EQ through AVAudioUnitEQ; an app that only routes to a Bluetooth device controls routing and volume, not the device's internal processing. ## Building the band sliders in SwiftUI Bind each slider to a band on a real EQ node so moving it changes sound, not just a number. `AVAudioUnitEQ` exposes an array of bands, each with a center frequency and a gain you set in decibels. ```swift let eq = AVAudioUnitEQ(numberOfBands: 6) let centers: [Float] = [60, 230, 910, 3000, 7000, 14000] for (i, f) in centers.enumerated() { eq.bands[i].filterType = .parametric eq.bands[i].frequency = f eq.bands[i].bandwidth = 1.0 eq.bands[i].bypass = false } // SwiftUI: Slider(value: $gain[i], in: -12...12) updates eq.bands[i].gain ``` Cover the audible range sensibly, roughly 20 Hz to 20,000 Hz, with bands spaced so each slider makes an audible difference. Six to ten bands is plenty; more sliders look impressive and help no one. ## Presets and balance Presets are just saved gain arrays, so model them as named structs the user can apply and tweak. A restaurant preset might cut low rumble and lift speech frequencies; a music preset might keep things flatter. Let users start from a preset and adjust, then save their own. For left-right balance, expose a single control that trims gain or volume per side, since hearing is rarely symmetric. The [anonymous voice changer pitch slider](/blogs/anonymous-voice-changer-pitch-slider-ui/) shows the same real-time slider-to-audio-parameter binding you will reuse here. ## Accessibility and honesty This screen is used by people tuning their hearing, so legibility is not optional. Never encode meaning in color alone; the [W3C guidance on use of color](https://www.w3.org/WAI/WCAG21/Understanding/use-of-color.html) applies directly, so pair any colored band indicator with a number and a label. Show gain in decibels and frequency in hertz so a user can describe their settings to an audiologist. Be honest about what the app is. A consumer EQ for comfort is useful, but it is not a hearing aid fitting and should not claim to correct a hearing loss. Keep the language to comfort and preference, and point users to a professional for clinical tuning. ## Common mistakes The biggest error is promising EQ over audio you do not control, such as the phone's system output or another app's sound; build against your own AVAudioEngine graph instead. Close behind is omitting decibel and hertz labels, which turns a precise tool into guesswork. Bluetooth adds latency, so do not pair this with a live-monitoring feature that expects instant feedback without accounting for the delay. And too many bands overwhelm the very users who need clarity. The [Bluetooth device pairing UI](/blogs/bluetooth-device-pairing-ui-swiftui/) covers the connection step that should come before any mixer screen appears. ## Building the screen fast The DSP is your work; the mixer layout is a known pattern worth starting from a design. [VP0](/explore) is a free, $0 iOS design library where each screen has a hidden source page an AI builder reads from a pasted link: ```text Build this iOS audio EQ screen in SwiftUI. Read the layout and tokens from this VP0 source page: . Lay out six vertical band sliders labeled in Hz with a dB readout, a preset row, and a left-right balance control. Bind each slider to an AVAudioUnitEQ band. Keep labels high-contrast and never rely on color alone. ``` You get the slider layout and presets from the design and connect them to your audio engine, so the effort stays on the sound. ## What to choose For a hearing comfort mixer, build the UI in SwiftUI with six to ten labeled vertical sliders, presets as saved gain arrays, and a per-side balance, then bind them to an `AVAudioUnitEQ` inside your own `AVAudioEngine` graph. Do not try to equalize system or other-app audio; route to Bluetooth devices with AVAudioSession and leave certified hearing-device tuning to Apple's accessibility features. Label everything in hertz and decibels, never rely on color alone, and keep the claims to comfort rather than clinical correction. Start the screen from a free VP0 design, generate it with Claude Code or Cursor, and test on real Bluetooth hardware where latency and routing behave differently than on the simulator. ## Frequently asked questions ### How do I build a Bluetooth hearing aid EQ mixer UI for iOS? Build the screen in SwiftUI as labeled vertical sliders, one per frequency band, with presets and a left-right balance, then bind each slider to a band on an AVAudioUnitEQ inside an AVAudioEngine graph so it shapes the audio your app plays. Label bands in hertz and gain in decibels. Start the layout from a free VP0 design with Claude Code or Cursor and connect it to your audio engine. ### Can an app control the EQ of any Bluetooth hearing aid? Not arbitrarily. Your app can fully equalize audio it plays itself through AVAudioUnitEQ, and it can route audio to a Bluetooth device through AVAudioSession. System-wide tuning of Made for iPhone hearing devices is handled by Apple's accessibility features, not by open app access to another app's or the system's output. Design for the audio you actually control. ### How many EQ bands should the mixer have? Six to ten bands spanning roughly 20 Hz to 20,000 Hz is plenty for a comfort EQ. Each slider should make an audible difference, so widely spaced parametric bands beat a long row of sliders that barely change the sound. Fewer, clearly labeled bands serve the people who need this screen better than a dense graphic curve. ### Is a hearing EQ app a medical device? Treat it as a comfort tool, not a medical hearing aid. Shaping the sound a user plays is fine, but claiming to correct a hearing loss or replace a clinical fitting invites both regulatory scrutiny and user harm. Keep the language to preference and comfort, label settings honestly, and direct users to an audiologist for clinical tuning. ### Where can I get a free template for the EQ screen? VP0 is a free iOS design library where each screen has an AI-readable source page, so you can browse a mixer or settings layout, copy its link, and have Claude Code or Cursor build it in SwiftUI. You supply the AVAudioEngine graph and band logic; the design gives you the slider layout, presets row, and balance control. ## Frequently asked questions ### How do I build a Bluetooth hearing aid EQ mixer UI for iOS? Build the screen in SwiftUI as labeled vertical sliders, one per frequency band, with presets and a left-right balance, then bind each slider to a band on an AVAudioUnitEQ inside an AVAudioEngine graph so it shapes the audio your app plays. Label bands in hertz and gain in decibels. Start the layout from a free VP0 design with Claude Code or Cursor and connect it to your audio engine. ### Can an app control the EQ of any Bluetooth hearing aid? Not arbitrarily. Your app can fully equalize audio it plays itself through AVAudioUnitEQ, and it can route audio to a Bluetooth device through AVAudioSession. System-wide tuning of Made for iPhone hearing devices is handled by Apple's accessibility features, not by open app access to another app's or the system's output. Design for the audio you actually control. ### How many EQ bands should the mixer have? Six to ten bands spanning roughly 20 Hz to 20,000 Hz is plenty for a comfort EQ. Each slider should make an audible difference, so widely spaced parametric bands beat a long row of sliders that barely change the sound. Fewer, clearly labeled bands serve the people who need this screen better than a dense graphic curve. ### Is a hearing EQ app a medical device? Treat it as a comfort tool, not a medical hearing aid. Shaping the sound a user plays is fine, but claiming to correct a hearing loss or replace a clinical fitting invites both regulatory scrutiny and user harm. Keep the language to preference and comfort, label settings honestly, and direct users to an audiologist for clinical tuning. ### Where can I get a free template for the EQ screen? VP0 is a free iOS design library where each screen has an AI-readable source page, so you can browse a mixer or settings layout, copy its link, and have Claude Code or Cursor build it in SwiftUI. You supply the AVAudioEngine graph and band logic; the design gives you the slider layout, presets row, and balance control. --- *Published on the [VP0 Journal](https://vp0.com/blogs). Free to read, index and cite with attribution.*